Rf energy delivery system and method

ABSTRACT

Devices, systems and methods are disclosed for the ablation of tissue. A steerable ablation catheter can include one or more ablation elements at its distal end and one or more ablation elements fixedly attached to its shaft. The distal end of the ablation catheter can be deflected to assume a number of different deflection geometries in at least one direction along the shaft. One feature of the ablation catheter is that its shaft can comprise materials of differing durometers or stiffnesses attached together at a joint. Methods associated with use of the ablation catheter are also covered.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of patent application Ser. No.13/906,762, filed May 31, 2013, entitled RF ENERGY DELIVERY SYSTEM ANDMETHOD, which claims priority to, U.S. patent application Ser. No.12/332,236, filed Dec. 10, 2008, entitled RF ENERGY DELIVERY SYSTEM ANDMETHOD, which application claims the benefit of U.S. ProvisionalApplication No. 61/007,016, filed Dec. 10, 2007, the entirety of both ofwhich is incorporated herein by reference.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The present invention relates generally to ablation systems and methodsfor performing targeted tissue ablation in a patient. In particular, thepresent invention provides catheters which deliver radiofrequency (RF)energy that create safe, precision lesions in tissue such as linearlesions created in cardiac tissue.

BACKGROUND OF THE INVENTION

Tissue ablation is used in numerous medical procedures to treat apatient. Ablation can be performed to remove undesired tissue such ascancer cells. Ablation procedures may also involve the modification ofthe tissue without removal, such as to stop electrical propagationthrough the tissue in patients with an arrhythmia condition. Often theablation is performed by passing energy, such as electrical energy,through one or more electrodes and causing the tissue in contact withthe electrodes to heat up to an ablative temperature. Ablationprocedures can be performed on patients with atrial fibrillation (AF) byablating tissue in the heart.

Mammalian organ function typically occurs through the transmission ofelectrical impulses from one tissue area to another. A disturbance ofsuch electrical transmission may lead to organ malfunction. Oneparticular area where electrical impulse transmission is critical forproper organ function is in the heart. Normal sinus rhythm of the heartbegins with the sinus node generating an electrical impulse that ispropagated uniformly across the right and left atria to theatrioventricular node. Atrial contraction leads to the pumping of bloodinto the ventricles in a manner synchronous with the pulse.

Atrial fibrillation refers to a type of cardiac arrhythmia where thereis disorganized electrical conduction in the atria causing rapiduncoordinated atrial contractions that result in ineffective pumping ofblood into the ventricle as well as a lack of synchrony. During AF, theatrioventricular node receives electrical impulses from numerouslocations throughout the atria instead of only from the sinus node.These aberrant signals overwhelm the atrioventricular node, producing anirregular and rapid heartbeat. As a result, blood may pool in the atria,increasing the likelihood of blood clot formation. The major riskfactors for AF include age, coronary artery disease, rheumatic heartdisease, hypertension, diabetes, and thyrotoxicosis. AF affects 7% ofthe population over age 65.

Atrial fibrillation treatment options are limited. Lifestyle changesonly assist individuals with lifestyle related AF. Medication therapymanages AF symptoms, often presents side effects more dangerous than AF,and fails to cure AF. Electrical cardioversion attempts to restore anormal sinus rhythm, but has a high AF recurrence rate. In addition, ifthere is a blood clot in the atria, cardioversion may cause the clot toleave the heart and travel to the brain (causing a stroke) or to someother part of the body. What are needed are new methods for treating AFand other medical conditions involving disorganized electricalconduction.

Various ablation techniques have been proposed to treat AF, includingthe Cox-Maze ablation procedure, linear ablation of various regions ofthe atrium, and circumferential ablation of pulmonary vein ostia. TheCox-Maze ablation procedure and linear ablation procedures are tediousand time-consuming, taking several hours to accomplish. Currentpulmonary vein ostial ablation is proving to be difficult to do, and haslead to rapid stenosis and potential occlusion of the pulmonary veins.All ablation procedures involve the risk of inadvertently damaginguntargeted tissue, such as the esophagus while ablating tissue in theleft atrium of the heart. There is therefore a need for improved atrialablation products and techniques that create efficacious lesions in asafe manner.

SUMMARY OF THE INVENTION

Several unique ablation catheters and ablation catheter systems andmethods are provided which map and ablate surface areas within the heartchambers of a patient, with one or few catheter placements. Anyelectrocardiogram signal site (e.g. a site with aberrant signals) orcombination of multiple sites that are discovered with this placementmay be ablated. In alternative embodiments, the ablation catheters andsystems may be used to treat non-cardiac patient tissue, such as tumortissue.

According to a first aspect of the invention, an ablation catheter forperforming a medical procedure on a patient is provided. The ablationcatheter comprises an elongate shaft with a proximal portion including aproximal end and a distal end, and a distal portion with a proximal endand a distal end. The elongate shaft further comprises a shaft ablationassembly and a distal ablation assembly configured to deliver energy,such as RF energy, to tissue. The shaft ablation assembly is proximal tothe distal end of the distal portion, and includes at least one shaftablation element fixedly attached to the shaft and configured to deliverablation energy to tissue. The distal ablation assembly is at the distalend of the distal portion and includes at least one tip ablation elementconfigured to deliver ablation energy to tissue.

In a preferred embodiment, the distal portion can be deflected in one ormore directions, in one or more deflection geometries. The deflectiongeometries may be similar or symmetric deflection geometries, or thedeflection geometries may be dissimilar or asymmetric deflectiongeometries. The shaft may include one or more steering wires configuredto deflect the distal portion in the one or more deflection directions.The elongate shaft may include different diameters along its length, andthe stiffness of the shaft may vary along its length. The elongate shaftmay include a guide plate within the shaft, the guide plate configuredto enhance the deflection (steering) of the distal portion, such as tomaintain deflections in a single plane. The shaft may include variablematerial properties such as a asymmetric joint between two portions, anintegral member within a wall or fixedly attached to the shaft, avariable braid, or other variation used to create multiple deflections,such as deflections with asymmetric deflection geometries.

In another preferred embodiment, the distal ablation assembly may befixedly attached to the distal end of the distal portion, or it may beadvanceable from the distal portion, such as via a control shaft. Thedistal ablation assembly may comprise a single ablation element, such asan electrode, or multiple ablation elements. The distal ablationassembly may include a carrier assembly of ablation elements, and thecarrier assembly may be changeable from a compact geometry to anexpanded geometry, such transition caused by advancement and/orretraction of a control shaft. The distal ablation assembly may includemultiple ablation elements which can be positioned to grab and/orsurround a portion of tissue, such as ablation elements on forked orscissor carrier arms.

The shaft ablation assembly may include a single ablation element ormultiple ablation elements, preferably three to six ablation elementsfixedly attached to the shaft. The ablation elements may have a profilethat is flush with the surface of the shaft, or more preferably theablation elements outer diameter is slightly greater than the shaftdiameter such that the ablation elements have improved contact withtissue during delivery of ablation energy.

The ablation elements of the present invention can deliver one or moreforms of energy, preferably RF energy. The ablation elements may havesimilar or dissimilar construction, and may be constructed in varioussizes and geometries. The ablation elements may include one or morethermocouples, such as two thermocouples mounted 180° from each other onan ablation element inner or outer surface. The ablation elements mayinclude means of dissipating heat, such as increased surface area ofprojecting fins. The ablation elements may have asymmetric geometries,such as electrodes with thin and thick walls positioned on the insideand/or outside of one or more curved deflection geometries. In apreferred embodiment, one or more ablation elements is configured in atubular geometry, and the wall thickness to outer diameter approximatesa 1:10 ratio. In another preferred embodiment, one or more ablationelements is configured to record, or map electrical activity in tissuesuch as mapping of cardiac electro grams. In yet another preferredembodiment, one or more ablation elements is configured to deliverpacing energy, such as to energy delivered to pace the heart of apatient.

The ablation catheters of the present invention may be used to treat oneor more medical conditions by delivering ablation energy to tissue.Conditions include an arrhythmia of the heart, cancer, and otherconditions in which removing or denaturing tissue improves the patient'shealth.

According to another aspect of the invention, a kit of ablationcatheters is provided. A first ablation catheter has a distal portionwhich can be deflected in at least two symmetric geometries. A secondablation catheter has a distal portion which can be deflected in atleast two asymmetric geometries.

According to another aspect of the invention, a method of treatingproximal or chronic atrial fibrillation is provided. An ablationcatheter of the present invention may be placed in the coronary sinus ofthe patient, such as to map electrograms and/or ablate tissue, andsubsequently placed in the left or right atrium to ablate tissue. Theablation catheter may be placed to ablate one or more tissue locationsincluding but not limited to: fasicals around a pulmonary vein; and themitral isthmus.

According to another aspect of the invention, a method of treatingatrial flutter is provided. An ablation catheter of the presentinvention may be used to achieve bi-directional block, such as byplacement in one or more locations in the right atrium of the heart.

According to another aspect of the invention, a method of ablatingtissue in the right atrium of the heart is provided. An ablationcatheter of the present invention may be used to: create lesions betweenthe superior vena cava and the inferior vena cava; the coronary sinusand the inferior vena cava; the superior vena cava and the coronarysinus; and combinations of these. The catheter can be used to map and/orablate the sinus node, such as to treat sinus node tachycardia.

According to another aspect of the invention, a method of treatingventricular tachycardia is provided. An ablation catheter of the presentinvention may be placed in the left or right ventricles of the heart,induce ventricular tachycardia by delivering pacing energy, and ablatingtissue to treat the patient.

According to another aspect of the invention, an ablation catheter witha first deflection geometry larger than a second deflection geometry isprovided. The ablation catheter is placed in the smaller seconddeflection geometry to ablate one or more of the following tissuelocations: left atrial roof; left atrial septum; tissue adjacent theleft atrial septum; and tissue adjacent the left atrial posterior wall.The ablation catheter is placed in the larger first deflection geometryto ablate at least the left atrial floor.

According to another aspect of the invention, an ablation catheter ofthe present invention is used to treat both the left and right atria ofa heart. The catheter is configured to transition to a deflectiongeometry with a first deflection geometry and a second deflectiongeometry, where the first deflection geometry is different than thesecond deflection geometry. The catheter is used to ablate tissue in theright atrium using at least the first deflection geometry and alsoablate tissue in the left atrium using at least the second deflectiongeometry.

According to a first aspect of the invention, a catheter for performinga medical procedure on a patient is provided. The catheter comprises anelongate shaft with a proximal portion including a proximal end and adistal end, and a distal portion with a proximal end and a distal end.The catheter further comprises a deflection assembly configured todeflect the distal portion in a first direction in a first geometry anda second direction in a second geometry, wherein the first and secondgeometries are different. The catheter further includes a functionalelement fixedly mounted to the distal portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which.

FIG. 1 illustrates a side view of an ablation catheter, consistent withthe present invention.

FIG. 1A illustrates a schematic view of an ablation system, consistentwith the present invention.

FIG. 2 illustrates an anatomical view of an ablation catheter placedinto the left atrium of a heart, consistent with the present invention.

FIG. 3A illustrates a side view of the distal portion of a shaft of anablation catheter, with a staircase joint, consistent with the presentinvention.

FIG. 3B illustrates a side, partial sectional view of the shaft of FIG.3A.

FIG. 3C illustrates a side view of an alternative tapered joint,consistent with the present invention.

FIG. 3D illustrates a side view of an alternative toothed joint,consistent with the present invention.

FIG. 4 illustrates a side view of an ablation catheter, consistent withthe present invention.

FIG. 4A illustrates a side view of the distal end of the ablationcatheter of FIG. 4.

FIG. 4B illustrated a cross sectional view of the shaft of the ablationcatheter of FIG. 4

FIG. 4C illustrates a side view of a preferred construction of a shaftsubassembly of the catheter of FIG. 4.

FIG. 4D illustrates a side sectional view of a portion of the shaftsubassembly of FIG. 4C.

FIG. 4E illustrates a cross sectional view of the catheter shaftsubassembly of FIG. 4C.

FIG. 5A illustrates a side view of two asymmetric deflection geometriesof the distal portion of a single catheter shaft, consistent with thepresent invention.

FIGS. 5B and 5C illustrate side and end views of a distal end of acatheter shaft, including a guide plate consistent with the presentinvention.

FIG. 6 is an exploded view of a handle of an ablation catheter,consistent with the present invention.

FIGS. 7 A and 7B illustrate end and side views, respectively, of apreferred shaft electrode, consistent with the present invention.

FIGS. 7C and 7D illustrate side and end views, respectively, of apreferred tip electrode, consistent with the present invention.

FIG. 7E illustrates a side sectional view of the distal end of acatheter shaft, consistent with the present invention.

FIG. 8A illustrates a side sectional view of the distal end of acatheter shaft, with an in-line shaft electrode, consistent with thepresent invention.

FIG. 8B illustrates an exploded view of FIG. 8A.

FIG. 9A illustrates a perspective view of a preferred configuration oftwo shaft electrodes, each with helical geometry, consistent with thepresent invention.

FIG. 9B illustrates a perspective view of a preferred configuration of ashaft electrode, with partial band geometry and fixedly mounted to acatheter shaft, consistent with the present invention.

FIG. 9C illustrates a perspective view of a preferred configuration of atip electrode, with square tip geometry, consistent with the presentinvention.

FIG. 9D illustrates a perspective view of a preferred configuration ofthree shaft electrodes with “S” shape geometry, and a tip electrode withflattened sides, consistent with the present invention.

FIGS. 9E and 9F illustrate side views of a preferred configuration oftwo shaft electrodes, each with non-uniform wall thickness, consistentwith the present invention.

FIGS. 9G and 9H illustrate side views of a preferred configuration oftwo tip electrodes, each with non-uniform wall thickness, consistentwith the present invention.

FIGS. 9J and 9K illustrate side and end views, respectively, of apreferred configuration of a tip electrode with eccentric wallthickness, consistent with the present invention.

FIG. 9L illustrates an end view of a preferred configuration of a shaftelectrode, with a projecting fin, consistent with the present invention.

FIG. 9M illustrates an end view of a preferred configuration of a shaftelectrode, with multiple projecting fins, consistent with the presentinvention.

FIGS. 9N and 9P illustrate side and end views, respectively, of apreferred configuration of a shaft electrode, with non-uniform wallthickness, consistent with the present invention.

FIG. 10 illustrates a side view of the distal portion of an ablationcatheter, with a malleable member incorporated into the shaft,consistent with the present invention.

FIGS. 11A and 11B illustrate side views of the distal portion of anablation catheter, in unexpanded and expanded states, respectively,consistent with the present invention.

FIGS. 12A and 12B illustrate side views of the distal portion of anablation catheter, in undeployed and deployed states, respectively,consistent with the present invention.

FIG. 13 illustrates a side sectional view of the distal portion of anablation catheter, consistent with the present invention.

FIG. 14 illustrates a side sectional view of the distal portion of anablation catheter, consistent with the present invention.

FIGS. 15, 15A, 15B, 15C, 15D, 15E and 15F illustrate numerous views ofan ablation catheter including a carrier assembly advanceable from thedistal end of the shaft, consistent with the present invention.

FIG. 16 illustrates a perspective view of the distal portion of anablation catheter including a carrier assembly configured in a forkedgeometry and advanceable from the distal end of the catheter shaft,consistent with the present invention.

FIGS. 17 A, 17B and 17C illustrate perspective views of the distalportion of an ablation catheter in deployed, partially deployed, andfully deployed states, respectively, consistent with the presentinvention.

FIGS. 18A, 18B, 18C and 18D illustrate various views of the distalportion of an ablation catheter including an expandable carrierassembly, consistent with the present invention.

FIGS. 19A, 19B, 19C, 19D and 19E illustrate various views of the distalportion of an ablation catheter including an expandable split shaft,consistent with the present invention.

FIGS. 20A and 20B illustrate side and perspective views, respectively,of the distal portion of an ablation catheter with a spiral carrier armand an elongate electrode, consistent with the present invention.

FIGS. 21A and 21B illustrate side and perspective views, respectively,of the distal portion of an ablation catheter with a spiral carrier armand multiple discrete electrodes, consistent with the present invention.

FIG. 22A illustrates a perspective view of the distal portion of anasymmetrically deflectable catheter shaft construction including one ormore wedges, consistent with the present invention.

FIG. 22B illustrates two unique bending geometries of the catheter shaftof FIG. 22A.

FIG. 23A illustrates a side view of the distal portion of anasymmetrically deflectable catheter shaft construction including one ormore wedges, consistent with the present invention.

FIGS. 23B and 23C illustrate two unique bending geometries of thecatheter shaft of FIG. 23A.

FIG. 24 illustrates a perspective view of an asymmetrically deflectablecatheter shaft construction including one or more slits, consistent withthe present invention.

FIG. 25 illustrates a side view of a catheter, including at least onetip functional element, at least of shaft functional element and adeflectable distal portion, consistent with the present invention.

FIG. 26A illustrates a side view of the distal portion of a shaftconfigured to deflect in two directions with two preferred symmetricdeflection geometries, consistent with the present invention.

FIG. 26B illustrates a side view of the distal portion of a shaftconfigured to deflect in two directions with two preferred symmetricdeflection geometries, consistent with the present invention.

FIG. 26C illustrates a side view of the distal portion of a shaftconfigured to deflect in two directions with two preferred asymmetricdeflection geometries, consistent with the present invention.

FIG. 26D illustrates a side view of a distal portion of a shaftconfigured to deflect in two directions with two preferred asymmetricdeflection geometries, consistent with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain specific details are set forth in the following description andfigures to provide an understanding of various embodiments of theinvention. Certain well-known details, associated electronics anddevices are not set forth in the following disclosure to avoidunnecessarily obscuring the various embodiments of the invention.Further, those of ordinary skill in the relevant art will understandthat they can practice other embodiments of the invention without one ormore of the details described below. Finally, while various processesare described with reference to steps and sequences in the followingdisclosure, the description is for providing a clear implementation ofparticular embodiments of the invention, and the steps and sequences ofsteps should not be taken as required to practice this invention.

The present invention provides catheters for performing targeted tissueablation in a subject. In preferred embodiments, the catheters comprisean elongate shaft having a proximal end and distal end and preferably alumen extending at least partially therebetween. The catheter ispreferably of the type used for performing intracardiac procedures,typically being introduced from the femoral vein in a patient's leg orfrom a vessel in the patient's neck. The catheter is preferablyintroducible through a sheath, such as a transeptal sheath, and alsopreferably has a steerable tip that allows positioning of the distalportion such as when the distal end of the catheter is within a heartchamber. The catheters include ablation elements located at the distalend of the shaft (tip electrodes), as well as ablation elements locatedon an exterior surface of the shaft proximal to the distal end (shaftelectrodes). The tip electrodes may be fixedly attached to the distalend of the shaft, or may be mounted on an advanceable and/or expandablecarrier assembly. The carrier assembly may be attached to a controlshaft that is coaxially disposed and slidingly received within the lumenof the shaft. The carrier assembly is deployable by activating one ormore controls on a handle of the catheter, such as to engage one or moreablation elements against cardiac tissue, typically atrial wall tissueor other endocardial tissue. The shaft may include deflection means,such as means operably connected to a control on a handle of thecatheter. The deflection means may deflect the distal portion of theshaft in one or more directions, such as deflections with two symmetricgeometries, two asymmetric geometries, or combinations of these.Asymmetries may be caused by different radius of curvature, differentlength of curvature, differences in planarity, other different 2-Dshapes, other different 3-D shapes, and the like.

In particular, the present invention provides ablation catheters withmultiple electrodes that provide electrical energy, such asradiofrequency (RF) energy, in monopolar (unipolar), bipolar or combinedunipolar-bipolar fashion, as well as methods for treating conditionssuch as paroxysmal atrial fibrillation, chronic atrial fibrillation,atrial flutter, supra ventricular tachycardia, atrial tachycardia,ventricular tachycardia, ventricular fibrillation, and the like, withthese devices.

The normal functioning of the heart relies on proper electrical impulsegeneration and transmission. In certain heart diseases (e.g., atrialfibrillation) proper electrical generation and transmission aredisrupted or are otherwise abnormal. In order to prevent improperimpulse generation and transmission from causing an undesired condition,the ablation catheters and RF generators of the present invention may beemployed.

One current method of treating cardiac arrhythmias is with catheterablation therapy. Physicians make use of catheters to gain access intointerior regions of the body. Catheters with attached electrode arraysor other ablating devices are used to create lesions that disruptelectrical pathways in cardiac tissue. In the treatment of cardiacarrhythmias, a specific area of cardiac tissue having aberrantconductive pathways, such as atrial rotors, emitting or conductingerratic electrical impulses, is initially localized. A user (e.g., aphysician) directs a catheter through a main vein or artery into theinterior region of the heart that is to be treated. The ablating element(or elements) is next placed near the targeted cardiac tissue that is tobe ablated. The physician directs energy, provided by a source externalto the patient, from one ore more ablation elements to ablate theneighboring tissue and form a lesion. In general, the goal of catheterablation therapy is to disrupt the electrical pathways in cardiac tissueto stop the emission and/or prevent the propagation of erratic electricimpulses, thereby curing the focus of the disorder. For treatment of AF,currently available methods and devices have shown only limited successand/or employ devices that are extremely difficult to use or otherwiseimpractical.

The ablation systems of the present invention allow the generation oflesions of appropriate size and shape to treat conditions involvingdisorganized electrical conduction (e.g., AF). The ablation systems ofthe present invention are also practical in terms of ease-of-use andlimiting risk to the patient (such as in creating an efficacious lesionwhile minimizing damage to untargeted tissue), as well as significantlyreducing procedure times. The present invention addresses this needwith, for example, arrangements of one or more tip ablation elements andone or more shaft ablation elements configured to create a linear lesionin tissue, such as the endocardial surface of a chamber of the heart, bydelivery of energy to tissue or other means. The electrodes of thepresent invention may include projecting fins or other heat dissipatingsurfaces to improve cooling properties. The distal portions of thecatheter shafts of the present invention may deflect in two or moresymmetric or asymmetric geometries, such as asymmetric geometries withdifferent radius of curvature or other geometric shape differences. Theablation catheters and RF generators of the present invention allow aclinician to treat a patient with AF in a procedure much shorter induration than current AF ablation procedures. The lesions created by theablation catheters and RF generators of the present invention aresuitable for inhibiting the propagation of inappropriate electricalimpulses in the heart for prevention of reentrant arrhythmias, whileminimizing damage to untargeted tissue, such as the esophagus or phrenicnerve of the patient.

Definitions. To facilitate an understanding of the invention, a numberof terms are generally defined below.

As used herein, the terms “subject” and “patient” refer to any animal,such as a mammal like livestock, pets, and preferably a human. Specificexamples of “subjects” and “patients” include, but are not limited, toindividuals requiring medical assistance, and in particular, requiringAF catheter ablation treatment.

As used herein, the terms “catheter ablation” or “ablation procedures”or “ablation therapy,” and like terms, refer to what is generally knownas tissue destruction procedures. Ablation is often used in treatingseveral medical conditions, including abnormal heart rhythms. It can beperformed both surgically and non-surgically. Non-surgical ablation istypically performed in a special lab called the electrophysiology (EP)laboratory. During this non-surgical procedure an ablation catheter isinserted into the heart using fluoroscopy for visualization, and then anenergy delivery apparatus is used to direct energy to the heart musclevia one or more ablation elements of the ablation catheter. This energyeither “disconnects” or “isolates” the pathway of the abnormal rhythm(depending on the type of ablation). It can also be used to disconnectthe conductive pathway between the upper chambers (atria) and the lowerchambers (ventricles) of the heart. For individuals requiring heartsurgery, ablation can be performed during coronary artery bypass orvalve surgery.

As used herein, the term “ablation element” refers to an energy deliveryelement, such as an electrode for delivering electrical energy. Ablationelements can be configured to deliver multiple types of energy, such asultrasound energy and cryogenic energy, either simultaneously orserially. Electrodes can be constructed of a conductive plate, cylinderor tube, a wire coil, or other means of conducting electrical energythrough contacting tissue. In unipolar energy delivery, the energy isconducted from the electrode, through the tissue to a ground pad, suchas a conductive pad attached to the back of the patient. The highconcentration of energy at the electrode site causes localized tissueablation. In bipolar energy delivery, the energy is conducted from afirst electrode to one or more separate electrodes, relatively local tothe first electrode, through the tissue between the associatedelectrodes. Bipolar energy delivery results in more precise, shallowlesions while unipolar delivery results in deeper lesions. Both unipolarand bipolar deliveries provide advantages, and the combination of theiruse is a preferred embodiment of this application.

As used herein, the term “carrier assembly” refers to a flexiblecarrier, on which one or more ablation elements are disposed. Carrierassemblies are not limited to any particular size, or shape, and can beconfigured to be constrained within an appropriately sized lumen.

As used herein, the term “carrier arm” refers to a wire-like shaftcapable of interfacing with electrodes and coupling to an advanceableand/or retractable control shaft. A carrier arm is not limited to anysize or measurement. Examples include, but are not limited to: stainlesssteel and other steel shafts; Nitinol shafts; titanium shafts;polyurethane shafts; and nylon shafts. Carrier arms can be entirelyflexible, or may include flexible and rigid segments. Carrier arms maybe radiopaque and/or include radiopaque or other visible markers, suchas a marker used to identify a particular carrier arm.

As used herein, the term “lesion,” or “ablation lesion,” and like terms,refers to tissue that has received ablation therapy. Examples include,but are not limited to, scars, scabs, dead tissue, burned tissue andtissue with conductive pathways that have been made highly resistive ordisconnected.

As used herein, the term “coagulum” refers to a blood mass or clot, suchas a clot which may be caused by excessive heating in blood.

As used herein, the term “return pad” refers to a surface electrodemounted to the patient's body, typically on the patient's back. Thereturn pad receives the RF ablation currents generated during unipolarpower delivery. The return pad is sized (large enough) such that thehigh temperatures generated remain within a few millimeters of thespecific ablation catheter's electrode delivering the unipolar power.

As used herein, the term “RF output” refers to an electrical outputproduced by the RF generator of the present invention. The RF output iselectrically connected to a jack or other electro-mechanical connectionmeans which allows electrical connection to one or more ablationelements (e.g. electrodes) of an ablation catheter. The RF outputprovides the RF energy to the ablation element to ablate tissue withbipolar and/or unipolar energy.

As used herein, the term “channel” refers to a pair of RF outputsbetween which bipolar energy is delivered. Each of the RF outputs in achannel may also deliver unipolar energy (simultaneous and/or sequentialto bipolar energy delivery), such as when a return pad is connected.

As used herein, the term “targeted tissue” refers to tissue to beablated, as identified by the clinician and/or one or more algorithms(e.g. algorithms of the system or algorithms otherwise available to theclinician). Lesions created in targeted tissue disconnect an aberrantelectrical pathway causing an arrhythmia, or treat other undesiredtissue such as cancer tissue.

As used herein, the term “untargeted tissue” refers to tissue which isdesired to avoid damage by ablation energy, such as the esophagus orphrenic nerve in an arrhythmia ablation procedure.

As used herein, the term “power delivery scheme” refers to a set ofablation parameters to be delivered during a set ablation time, and usedto safely create an effective lesion in targeted tissue. Power deliveryscheme parameters include but are not limited to: type (bipolar and/orunipolar) of energy delivered; voltage delivered; current delivered;frequency of energy delivery; duty cycle parameter such as duty cyclepercentage or length of period; field parameter such as configuration offields or number of fields in set that repeats; and combinationsthereof.

As used herein, the term “proximate” is used to define a particularlocation, such as “ablating tissue proximate the sinus node”. For thepurpose of this application, proximate shall include the areaneighboring a target as well as the target itself. For the exampleabove, the tissue receiving the ablation energy would be tissueneighboring the sinus node as well as the sinus node itself.

As used herein, the term “radius of curvature” is used to define theradius of a curved section of a deflectable distal portion of anablation catheter. Deflectable distal portions may include complexcurves, wherein the radius of curvature is an approximation of the curveof the entire distal portion when deflected. Distal portions may deflectin multiple planes, and the radius of curvature may represent theapproximate radius when the multi-planar deflection is projected onto asingle plane.

The present invention provides structures that embody aspects of theablation catheter. The present invention also provides RF generators forproviding ablation energy to the ablation catheters. The illustrated andpreferred embodiments discuss these structures and techniques in thecontext of catheter-based cardiac ablation. These structures, systems,and techniques are well suited for use in the field of cardiac ablation.

However, it should be appreciated that the invention is applicable foruse in other tissue ablation applications such as tumor ablationprocedures. For example, the various aspects of the invention haveapplication in procedures for ablating tissue in the prostrate, brain,gall bladder, uterus, and other regions of the body, preferably regionswith an accessible wall or flat tissue surface, using systems that arenot necessarily catheter-based. In a preferred embodiment, the targettissue is tumor tissue.

The ablation catheters and systems of the present invention haveadvantages over previous prior art devices. FIGS. 1-26 show variouspreferred embodiments of the ablation catheters and systems of thepresent invention. The present invention is not limited to theseparticular configurations.

Referring now to FIG. 1, one embodiment of an ablation catheter of thepresent invention is illustrated. Ablation catheter 100 includesflexible shaft 110. Handle 150 can be located on a proximal end theshaft and can include multiple controls, such as knob 151 and button152. Button 152 can be configured to initiate and/or discontinuedelivery of energy to one or more ablation elements located in a distalportion of the shaft. Knob 151 can be configured, when rotated, to causethe distal portion to deflect in one or more directions, such as tocurve in one direction when rotated clockwise, and to curve in anotherdirection when rotated counter-clockwise. In one embodiment, describedin detail below, knob 151 can be attached to two steering wires whichare captured in the distal portion and cause bi-directional steeringsuch as symmetric or asymmetric steering. In alternative embodiments, 1,3, 4 or more steering wires may be incorporated, such as steering wiresseparated by 120° or 90°, causing deflection in a single plane, or threeor more planes. Each deflection may have a simple geometry such as asingle plane, fixed radius curve, or more complex geometries.

Additional controls may be integrated into handle 150 to performadditional functions. A connector, not shown, can be integral to handle150 and allows electrical connection of ablation catheter 100 to one ormore separate devices such as an RF generator or other energy deliveryunit; a temperature monitoring system, an ECG monitoring system; acooling source; an inflation source, and/or numerous otherelectro-mechanical devices.

A distal portion of the shaft can include shaft ablation assembly 120having multiple ablation elements, such as ablation elements 121 a, 121b, 121 c and 121 d. The shaft can further include distal ablationassembly 130, which preferably includes at least one ablation element,such as an atraumatic (e.g. rounded tip), platinum, tip electrodeconfigured to deliver RF energy to tissue. In a preferred configuration,ablation elements 121 a, 121 b, 121 c and 121 d are platinum electrodesconfigured to deliver unipolar energy (energy delivered between thatelectrode and a return pad), and/or bipolar energy (energy deliveredbetween that electrode an a second electrode in general proximity to thefirst electrode). Distal ablation assembly 130 may include multipleablation elements, such as multiple platinum electrodes separated by aninsulator, and/or deployable from the distal end of shaft 110 (e.g. viaa control on handle 150). Distal ablation assembly 130 and shaftablation assembly 120 can further include one or more temperaturesensors (not shown), such as at least one thermocouple mounted to eachablation element. The temperature sensors can also be integrally formedwith the distal and shaft ablation assemblies.

In one embodiment, the ablation elements of catheter 100 can beelectrodes attached to signal wires traveling within shaft 110 andelectrically connecting to an electrical connector on handle 150. Thesignal wires, described in detail in reference to subsequent figures,can carry power to the electrodes for unipolar and/or bipolar energydelivery, and also can receive signals from the electrodes, such as ECGmapping signals of the human heart. The signal wires can also transmitor receive information from one or more other functional elements ofcatheter 100, such as a sensor (e.g., a thermocouple), or a transducer(e.g., an ultrasound crystal).

In one configuration, two signal wires of approximately 36 gauge can beconnected to a tip electrode of distal ablation assembly 130. The two 36gauge wires can each simultaneously deliver unipolar energy to the tipelectrode, such as up to 45 watts of unipolar energy (approximately 45Watts being a preferred maximum energy delivery for a tip electrode ofthe present invention). Minimizing of the diameter of the signal wiresprovides numerous advantages, such as minimizing the required diameterof shaft 110 as well as preventing undesired stiffening of shaft 110. Inan alternative embodiment, one or both of the 36 gauge wires can beconfigured to prevent embolization of the tip electrode, such as whenthe joint between the tip electrode and shaft 110 fails. One or both ofthese signal wires can be attached to a temperature sensor such as athermocouple and transmit temperature information back to an electricalconnector of handle 150, as described above.

In one configuration, a signal wire of approximately 36 gauge and asignal wire of approximately 40 gauge are connected to a shaft electrodesuch as shaft ablation element 121 a, 121 b, 121 c or 121 d. Bipolar orunipolar energy can be delivered through the 36 gauge wire, such as apower up to 20 watts (approximately 20 Watts being a preferred maximumenergy delivery for a shaft electrode of the present invention).Minimizing of the diameter of the signal wires provides numerousadvantages such as minimizing the required diameter of shaft 110 as wellas preventing undesired stiffening of shaft 110. One or both of thesesignal wires can be attached to a temperature sensor such as athermocouple and transmit temperature information back to an electricalconnector of handle 150.

Referring now to FIG. 1A, a preferred embodiment of an ablation systemof the present invention is illustrated. System 10 can include anablation catheter 100 and an energy delivery system, such as RFgenerator 190. Ablation catheter 100 can be attached to ECG interface191, such as at handle 150, which in turn can be attached to RFgenerator 190. RF generator is preferably an RF generator configured todeliver unipolar and bipolar RF energy to the ablation elements ofablation catheter 100. ECG Interface 191 can also be attached to ECGmonitor 192 such that the high power energy delivered to ablationcatheter 100 by RF generator 190 is isolated from ECG monitor 192. RFgenerator 190 can be connected to a power source (such as an electricaloutlet connected to 110 or 220 AC volts) and can be configured todeliver unipolar and bipolar RF energy to one or more electrodes ondistal ablation assembly 130 and shaft ablation assembly 120. RFgenerator 190 can also be attached to a return pad or ground electrode,such as patient return electrode 193, which is configured to receive theunipolar energy delivered to one or more ablation elements of catheter100.

Alternatively or additionally, RF generator 190 may deliver other formsof energy, including but not limited to: acoustic energy and ultrasoundenergy; electromagnetic energy such as electrical, magnetic, microwaveand radio frequency energies; thermal energy such as heat and cryogenicenergies; chemical energy; light energy such as infrared and visiblelight energies; mechanical energy; radiation; and combinations thereof.

In one embodiment, RF generator 190 can provide ablation energy to oneor more ablation elements of catheter 100 by sending power to one ormore independently controlled RF outputs of RF generator 190. Theindependent control of each RF output can allow a unique, programmablepower delivery signal to be sent to each electrode of ablation catheter100. The independent control of each RF output can further allow unique(independent) closed loop power delivery, such as power deliveryregulated by tissue temperature (e.g. regulated to tissue temperature of60° C.) information received from one or more temperature sensorsintegral to the attached ablation catheter and/or from sensors includedin a separate device.

The number of RF outputs can vary as required by the design of theattached ablation catheter. In one embodiment, four to twelveindependent RF outputs are provided, such as when the system of thepresent invention includes a kit of ablation catheters including atleast one catheter having from four to twelve electrodes. In anotherembodiment, sixteen or more independent RF outputs are provided, such aswhen the system of the present invention includes a kit of ablationcatheters including at least one catheter with sixteen or moreelectrodes.

Unipolar delivery can be accomplished by delivering currents that travelfrom an RF output of RF generator 190 to an electrically attachedelectrode of ablation catheter 100, through tissue to return pad 193,and back to RF generator 190 to which return pad 193 has been connected.Bipolar delivery can be accomplished by delivering current between afirst RF output which has been electrically connected to a firstelectrode of an ablation catheter and a second RF output which has beenelectrically connected to a second electrode of the ablation catheter,the current traveling through the tissue between and proximate the firstand second electrodes. Additionally, a combo mode energy delivery caninclude delivery of both bipolar energy and unipolar energysimultaneously. Combo mode energy delivery can be accomplished bycombining the unipolar and bipolar currents described immediately above.The user (e.g. a clinician or clinician's assistant) may select ordeselect RF outputs receiving energy to customize therapeutic deliveryto an individual patient's needs.

In another embodiment, five different pre-set energy delivery optionscan be provided to the user: unipolar-only, bipolar-only, and 4:1, 2:1and 1:1 bipolar/unipolar ratios. A bipolar-only option provides theshallowest depth lesion, followed by 4:1, then 2:1, then 1:1 and thenunipolar-only which provides the deepest depth lesion. The ability toprecisely control lesion depth increases the safety of the system andincreases procedure success rates as target tissue can be ablated nearor over important structures. In an alternative embodiment, currents canbe delivered in either unipolar mode or bipolar mode only. The preferredembodiment, which avoids bipolar-only, has been shown to providenumerous benefits including reduction of electrical noise generated byswitching off the return pad circuit (e.g. to create bipolar-only mode).

In another embodiment, RF generator 190 can include multiple independentPID control loops that utilize measured tissue temperature informationto regulate (i.e. provide closed loop) energy delivered to an ablationcatheter's electrodes. In one embodiment, RF generator 190 can includetwelve separate, electrically-isolated temperature sensor inputs. Eachtemperature input can be configured to receive temperature informationsuch as from a sensor (e.g., a thermocouple). The number of temperatureinputs can vary as required by the design. In one embodiment, four totwelve independent inputs can be provided, such as when the system ofthe present invention includes a kit of ablation catheters including atleast one catheter having four to twelve thermocouples. In anotherembodiment, sixteen or more independent temperature inputs can beprovided, such as when the system of the present invention includes akit of ablation catheters having at least one catheter with sixteen ormore thermocouples.

Ablation target temperatures can be user-selectable and automaticallyachieved and maintained throughout lesion creation, regardless of bloodflow conditions and/or electrode contact scenarios. Temperature targetinformation can be entered via a user interface of RF generator 190. Theuser interface can be configured to allow an operator to input systemparameter information including but not limited to: electrode selection;power delivery settings, targets and other power delivery parameters;and other information. The user interface can be further configured toprovide information to the operator, such as visual and audibleinformation including but not limited to: electrode selection, powerdelivery parameters and other information. Automatictemperature-controlled lesion creation provides safety and consistencyin lesion formation. Typical target temperature values made available tothe operator range from 50 to 70° C.

In one embodiment, a kit of the present invention includes a firstcatheter with asymmetric two-way deflection geometries and a secondcatheter with symmetric two-way deflection geometries. Additionalablation catheters may be included in the system of the presentinvention, such as ablation catheters configured to: create linearlesions; create lesions proximate pulmonary vein ostia; create lesionson the septum between the left and right atrium; ablation catheterswhich include multiple carrier arms each with at least one electrode;other ablation catheters; and combinations of these.

Referring now to FIG. 2, a method of the present invention isillustrated. For the purposes of FIG. 2, it is generally noted that alldesigns shown may include multiple electrodes, and in preferredconfigurations may also include a return pad (a large surface areaelectrode often attached to the patient's back). At least one pair ofelectrodes, and often many pairs, may be activated or powered withappropriately-powered potential differences to create RF waves thatpenetrate and ablate desired tissue. If the powering occurs between apair of electrodes, it is termed “bipolar”. If the powering occursbetween one electrode and the return pad, it is termed “unipolar”. Ifboth bipolar and unipolar power is delivered simultaneously to tissue,it is termed “combo” or “combo mode”.

The cross-section of the human heart depicts the atrioventricular nodeAV and the sinoatrial node SA of the right atrium RA, the pulmonary veinostia of the left atrium LA, and the septum with the right atrium RA andthe left atrium LA. Catheter 100 is shown entering the right atrium RA,passing through the septum, and terminating in left atrium LA. Thedistal portion of shaft 110 includes shaft ablation assembly 120 anddistal ablation assembly 130 as shown in FIG. 2. Distal ablationassembly 130 preferably includes a platinum electrode at its tip. Shaftablation assembly 120 preferably includes two to six (or more) platinumelectrodes secured to the outer diameter of shaft 110. The electrodes ofdistal ablation assembly 130 and shaft ablation assembly 120 may beconfigured to deliver unipolar and bipolar RF energy to the hearttissue, such as the tissue of the left atrium LA.

Catheter 100, provided in a sterile form such as via e-beamsterilization and sterile packaging, can be percutaneously inserted ineither femoral vein, advanced toward the heart through the inferior venacava (lVC), and into the right atrium. Through the use of a previouslyplaced transeptal sheath (e.g. a deflectable or fixed shape 9.5 Frsheath), catheter 100 may be advanced through the septum into the leftatrium LA to perform a left atrial ablation. In an alternativeembodiment, catheter 100 may be advanced only into the right atrium RAto perform an ablation procedure in the right atrium RA or coronarysinus.

In another method, ablation catheter 100 can be configured to treatparoxysmal atrial ablation and/or chronic atrial ablation. In theseprocedures, catheter 100 can be used as a reference catheter configuredto map electrical activity in the coronary sinus. Alternatively oradditionally, ablation catheter 100 may perform an ablation in the rightatrium RA or left atrium LA, such as an ablation of: the fasicalsproximate the pulmonary veins; the mitral isthmus; and other rightatrial RA and left atrial LA locations. In one embodiment, ablationcatheter 100 can be configured to be transformed into multipledeflection geometries such that the left and/or right atria can betreated utilizing one or more of these multiple deflection geometries.For example, the ablation catheter can be controlled to assume a firstdeflection radius (e.g. a radius less than or equal to 28 mm) to ablatea first tissue region, such as the “roof” of the left atrium, tissueproximate the septum, and/or tissue close to the posterior wall. Theablation catheter can then be controlled to assume a second deflectionradius to ablate a second tissue region, such as the floor of the leftatrium, for example. The second deflection radius can be smaller orlarger than the first deflection radius (e.g. less than or greater than28 mm).

In another method, a small deflection radius can be used to treat atriawith a relatively small volume, and a larger deflection radius can beused to treat larger atria (e.g. an enlarged atria of a chronic AFpatient). In yet another preferred method, an ablation catheter can beconfigured to treat the right atrium with a first deflection geometryand the left atrium with a second deflection geometry different than thefirst deflection geometry. Differences in deflection geometry mayinclude different radius of curvature, such as a first radius ofcurvature less than or equal to 28 mm and a second radius of curvaturegreater than or equal to 28 mm.

Ablation catheter 100 may include a handle with a rotating knob. Therotating knob may be operably connected to one or more steering wiressuch that rotation of the knob in a first direction causes the firstradius to be formed and rotating the knob in an opposite directioncauses the second radius to be formed.

In another method, ablation catheter 100 may be used to treat atrialflutter. The ablation procedure may be completed with as little as oneor two catheter placements allowing the operator to block the aberrantsignals causing the flutter. In one method, ablation catheter 100 blocksthe aberrant signals with less than 5 placements, preferably less than 3placements. In another preferred method, the ablation procedure resultsin bi-directional block. Ablation catheter 100 may be used to treatatrial flutter by creating a lesion along the length of the isthmus,such as with a single ablation. Alternatively or additionally, a lesionmay be created proximate the tricuspid annulus, a location known tooften include aberrant electrical signals associated with atrialflutter. In another embodiment, ablation catheter 100 can include adeflectable portion which can be deflected in a first direction with afirst radius of curvature, and in a second direction with a second,larger radius of curvature. The smaller first radius of curvature can beused to ablate the concave portion of the isthmus, and the larger secondradius of curvature can be used to create one or more lesions in thetissue proximate the tricuspid annulus. In one embodiment, the smallerradius of curvature can be at or below 28 mm and the larger radius ofcurvature can be at or above 28 mm.

Alternatively or additionally, ablation catheter 100 may be used inother methods to treat atrial flutter. In one embodiment, in a firststep, the distal portion of ablation catheter 100 can be placedrelatively perpendicular to the isthmus, such as with the middle portionof the shaft ablation assembly at a point along the isthmus; in a secondstep pacing energy can be applied by one or more tip ablation elementswhile electro grams are recorded by one or more shaft ablation elements;and in a third step pacing energy can be applied by one or more shaftablation elements while electro grams are recorded by one or more tipablation elements. Steps 2 and 3 may be repeated until desired electrograms are recorded. In an alternative embodiment, step 3 is performedbefore step 2. Alternatively or additionally, shaft ablation assembly120 can include multiple ablation elements, such as multiple electrodesconfigured to both deliver RF energy and record electro grams. Oneelectrode can be most proximate the proximal end of ablation catheter100, and one or more electrodes (“middle electrodes”) can be locatedbetween this most proximate electrode and the distal ablation assembly130. These one or more middle electrodes can be used to measure “splitpotential” electro grams, such as electro grams used to confirm adequateblock has been achieved. These middle electrodes can be used to identifytissue needing further ablation.

Alternatively or additionally, ablation catheter 100 may be used in yetother methods to treat atrial flutter. In one embodiment, in a firststep, the distal portion of ablation catheter 100 can be deflected 90°or more, such as a deflection of 135° or more (deflections not shown forease of illustration). The one or more ablation elements of shaftablation assembly 120 and/or distal ablation assembly 130 can be used todeliver ablation energy to tissue proximate the eustachian ridge and/orvalley. In one embodiment, ablation catheter 100 includes a deflectionmechanism (as described in various embodiments below), and the 90° ormore deflection can be accomplished by an operator activating thedeflection mechanism, such as via a control on a handle 150 of ablationcatheter 100 (handle and control not shown but described in detail inreference to various embodiments herein). Alternatively or additionally,the 90° or more deflection can be accomplished by pressing the distalportion of ablation catheter 100 against tissue, such as tissueproximate the eustachian ridge and/or valley.

Ablation catheter 100 may be used in various ablation procedures in theright atrium RA of the heart. In a preferred method, a lesion can becreated between one or more of: the superior vena cava (SVC) and theinferior vena cava (IVC); the coronary sinus (CS) and the IVC; and theSVC and the IVC. In one embodiment, a lesion can be created between allthree locations described immediately above. In another right atrialmethod, ablation catheter 100 can be used to treat sinus nodetachycardia by measuring electro grams in tissue proximate the sinusnode and ablating tissue proximate the sinus node.

Ablation catheter 100 may be used to ablate tissue proximate or withinthe coronary sinus (CS). In a preferred method, ablation catheter 100can deliver bipolar RD energy, such as to improve the treatment ofatrial fibrillation (e.g. improving acute and/or chronic results of AFtherapy).

Ablation catheter 100 may also be used to treat ventricular tachycardia.In one method, the distal portion of ablation catheter 100 can be placedin the right or left ventricle, and pacing energy can be delivered byone or more ablation elements, such as electrodes, to induce ventricletachycardia. Information received or determined by the pacing step canbe used by an operator to deliver ablation energy to the ventricle withone or more ablation elements of ablation catheter 100. The informationmay be used to selectively ablate tissue, such as to determine ablationlocation(s), ablation settings, or another ablation parameter.

The ablation catheter 100 of the present invention is preferablyconfigured to create linear or segmented linear lesions in tissue of apatient, such as heart tissue. The catheter may be further configured toablate tissue in an arrhythmia treating procedure such as a procedure totreat AF. Ablation catheter may be used in combination with otherablation catheters, such as catheters configured to be used prior toablation catheter 100 and/or catheters configured to create longer orotherwise larger lesions in tissue such as the left atrium LA. In thissubsequent use, ablation catheter 100 may be configured to createsmaller lesions that complete a set of lesions to treat AF. Thesesmaller lesions are often referred to as “touch up” lesions.

Ablation catheter 100 and the other ablation catheters of the presentinvention may be configured to ablate tissue and also map electricalactivity in tissue, such as intracardiac electrogram activity. Mappingof AF in humans has shown that areas of complex fractionated atrialelectro grams (CF AEs) correlate with areas of slowed conduction andpivot points of reentrant wavelets. Ablation catheter 100, or a systemof multiple ablation catheters which include ablation catheter 100, maybe used to both identify the areas with AF wavelets reenter, as well asselectively ablate these areas causing wavelet reentry to stop andprevent the perpetuation of AF. Mapping may be performed by one or moreablation elements of ablation catheter 100, such as ablation elementscomprising electrodes configured to deliver RF energy. In an alternativeembodiment, one or more ablation elements of catheter 100 are furtherconfigured to deliver pacing energy, such as electrical energyconfigured to pace one or more portions of a human heart.

Referring now to FIGS. 3A and 3B, an ablation catheter of the presentinvention is illustrated. In FIG. 3A, a side-view of a distal portion ofcatheter shaft 110 is shown. A proximal section 110 a can have a largerdiameter (e.g. 9 Fr) than a distal section 110 b (e.g. 7 Fr). Inaddition, the proximal section can be stiffer (e.g. by using stiffermaterial such as 7233 durometer Pebax) than the distal section (e.g.Pebax of 3533 durometer). Shaft 110 is preferably made of one or morebiocompatible materials commonly used in catheter construction, suchthat shaft 110 can be percutaneously introduced to the heart or otherlocation within the body of a patient. Shaft 110 may be a laminateconstruction, such as a structure including: braiding such as stainlesssteel braid; embedded or attached members such as stiffeners andmalleable (plastically deformable) members; liners such as Teflon linerswhich provide a low-friction surface for sliding members within shaft110; and elongate tubes which reside within shaft 110.

As shown, the proximal section of the catheter shaft can transition froma larger size (e.g., 9 Fr) to a smaller size (e.g., 7 Fr) at taperedjoint 113. In a preferred manufacturing method, a larger (e.g., 9 Frtube), a smaller (e.g., 7 Fr tube), and a tapered tube which tapers fromthe larger size to the smaller size are bonded together, such as viaheat bonding, adhesive bonding, or a combination of the two.

Also shown in FIG. 3A is a “staircase joint” 112 joining the proximaland distal sections, in which shaft 110 tapers or transitions from astiffer material (e.g. 7233 durometer Pebax) to a more flexible material(e.g. 3533 durometer Pebax). Staircase joint 112 can include an overlapof the stiffer material with the more flexible material, such as withthe two materials overlapping each other as shown in FIG. 3A. Staircasejoint 112 may be constructed by cutting the step profile into two tubesof different stiffness and thermally bonding the two steps together.Alternatively or additionally, adhesive may be used. Staircase joint 112provides a “hinge point” for deflection (steering), such as a deflectioncaused by advancement and/or retraction of a steering wire, not shownbut described in detail in reference to subsequent figures below.Staircase joint 112 may include an inserted elongate member, such as anelastically biased member of Nitinol wire or stainless steel wire, or amalleable member. Steering of shaft 110 is typically 90° or more. Joint112 can avoid the need for creating a hinge point with a collar in thewall of and/or within a lumen of shaft 110. Joint 112 can also beconfigured such that deflection toward the stiffer material (i.e.towards the top of the page in FIG. 3A), is less (e.g. less curvatureand greater radius of curve) than the deflection toward the moreflexible material (i.e. towards—the bottom of the page in FIG. 3B).Numerous other geometries of joints which joint two dissimilar materialsarranged to cause asymmetric deflection geometries may be incorporated,such as tapered joint 112′ of FIG. 3C which includes a continuous taperbetween the two materials, and joint 112″ of FIG. 3D which includes a“toothed” joint construction.

The catheter shaft of FIG. 3A can be constructed in numerous shapes andsizes. In one preferred embodiment, the distance from joint 112 to thedistal tip of the shaft can be approximately 2″, the size of joint 112can be approximately 0.7″, the distance from the distal end of taper 113to joint 112 can be approximately 1″, and the size of taper 113 can beapproximately 0.2″, for example.

Alternatively or additionally, shaft 110 may be modified with astiffening member, not shown but located within the wall of or attachedproximate an inner or outer wall of shaft 110, such as to createasymmetric deflection during steering and/or to provide a restoringforce (e.g. a force configured to straighten or curve the distal portionof shaft 110). The stiffening member may be maintained proximate toshaft 110 with a braid or a liner. In one embodiment, an elasticstiffener can be attached to one side of shaft 110, such that deflectiontoward that side is less than deflection toward the opposite site. Inanother embodiment, a plastically deformable stiffener can be similarlyattached, such that one or more curved shaped can be maintained until arestoring force is applied. Alternatively or additionally, shaft 110 mayinclude an eccentric braid (absent or reduced in a portion of the fullinner diameter of shaft 110), such that deflection toward the stifferpart of the braid is less than deflection toward the less stiff braidportion.

Referring back to FIG. 3A, an ablation element, such as tip electrode131, can be positioned the distal end of shaft 110. Tip electrode 131 ispreferably made of platinum and designed to have an atraumatic leadingedge (such as to prevent perforation of the left atrium or othersensitive heart tissue). Tip electrode 131 can be adhesively bonded toshaft 110, and may further include a reduction of (including a portionof) its internal diameter such as via a crimp or swage on its proximalend to increase the attachment force to shaft 110. In an alternativeembodiment, tip electrode 131 and the distal end of shaft 110 may havereverse, mating tapers (e.g., a “Chinese finger grip”) such that anapplied tension force causes increased attachment force. A crimp, swageor other geometry modification can also perform the function of removinga sharp edge on a tip (or shaft) electrode. Tip electrode 131 preferablyhas a length of 1 to 8 mm, and more preferably has a length ofapproximately 4 mm. Tip electrode 131 preferably has an inner diameterof 0.020″ to 0.300″ and more preferably has an inner diameter ofapproximately 0.094″. Tip electrode 131 typically has a surface area ofapproximately 33.7 mm², and preferably has a wall thickness of between0.006″ and 0.010″, typically between 0.008″ and 0.010″. In analternative embodiment, tip electrode 131 has a wall thickness between0.002″ and 0.020″.

Proximal to tip electrode 131 can be a series of electrodes such asshaft electrodes 121. In a preferred embodiment, 2 to 6 shaft electrodesare included. In an alternative embodiment, a single shaft electrode isattached to shaft 110. Shaft electrodes 121 have an inner diameterconfigured to allow adhesive attachment of electrodes 121 to shaft 110(e.g. closely matched diameters). In one embodiment, one or both of theends of electrodes 121 are swaged or crimped to increase the attachmentforce to shaft 110. The outer diameter of shaft electrodes 121 may besized to be flush with the outer diameter of shaft 110, or in anotherembodiment, the outer diameter of shaft electrodes 121 can be slightlylarger than the outer diameter of shaft 110 such that increasedengagement with tissue can be achieved. In an alternative embodiment,shaft 110 includes a recessed portion on its outer diameter where shaftelectrodes 121 can be attached. Shaft electrodes 121 preferably have alength of 1 to 8 mm, and more preferably have a length of approximately2 mm. Shaft electrodes 121 preferably have a diameter of 0.020″ to0.300″ and more preferably have a diameter of approximately 0.094″ (e.g.when shaft 110 has a diameter of 0.090″). Shaft electrodes 121 typicallyhave a surface area of approximately 29.5 mm², and preferably have awall thickness of between 0.006″ and 0.010″, typically between 0.008″and 0.010″. The shaft electrodes may also have similar or dissimilargeometries and/or materials of construction. In one embodiment, theshaft electrodes can be of different lengths or different thicknesses.

The shaft electrode 121 closest to tip electrode 131 (i.e., the distalmost shaft electrode) can be located approximately 1 to 8 mm from tipelectrode 131, and more preferably 3 mm. The separation between shaftelectrodes 121 is preferably 1 to 8 mm, and more preferably 3 mm. Eachof the ablation elements mounted on shaft 110, is preferably a platinumelectrode configured to deliver unipolar energy or bipolar energy (e.g.bipolar energy between adjacent electrodes or any pair of electrodes.Alternatively or additionally, one or more ablation elements may be anelectrode constructed of platinum-iridium, gold, or other conductivematerial. Alternatively or additionally, the ablation elements maydeliver another form of energy, including but not limited to: soundenergy such as acoustic energy and ultrasound energy; electromagneticenergy such as electrical, magnetic, microwave and radiofrequencyenergies; thermal energy such as heat and cryogenic energies; chemicalenergy; light energy such as infrared and visible light energies;mechanical energy; radiation; and combinations thereof.

Shaft electrodes 121 and tip electrode 131 preferably include at leastone temperature sensor such as a thermocouple. In one embodiment, eachelectrode can include at least two thermocouples, such as twothermocouples mounted (e.g. welded) to the inner diameter of eachelectrode and separated by 180°. In an alternative embodiment, three ormore thermocouples can be mounted to the inner diameter of one or moreelectrodes, such as the thermocouples being mounted at locationsequidistant from each other. In another alternative embodiment, two ormore thermocouples can be mounted in an eccentric geometry, such as ageometry relating to one or more particular deflection geometries of theshaft (e.g., a first thermocouple located on the outside of the curve ofa first deflection geometry and a second thermocouple located on theoutside of the curve of a second deflection geometry). In anotherembodiment, one or more thermocouples can be potted into an electrodewall such that the thermocouple is in direct contact with tissue duringablation. One or all of the thermocouples can be mounted, welded, glued,or attached within holes or openings in the electrode wall. In thisparticular embodiment, the thermocouple(s) can be flush with or reachbeyond the outer diameter of the electrodes and extend through theopenings in the electrodes into the catheter shaft. Signal wires, notshown, attach to the electrodes as well as the thermocouples, fordelivering energy to the electrodes as well as transmitting informationsignals (e.g. temperature levels) back to the handle of the ablationcatheter to which shaft 110 is attached.

Referring now to FIG. 3B, a partial cross-section of catheter shaft 110of FIG. 3A is shown. In order to generate the asymmetric deflectiondescribed in reference to FIG. 3A (noting that staircase joint 112 isnot shown), two steering wires 115 are included within the shaft 110. Inthe larger diameter portion (e.g. 9 Fr portion), steering wires 115“free float” within a lumen of shaft 110. At a point distal to taperedjoint 113, the steering wires 115 are fixedly attached to or embeddedwithin shaft 110 (e.g. between a braid and shaft 110 and/or between aliner and shaft 110, braid and liner not shown but described in detailin description of subsequent figures herebelow). This configuration ofthe steering wires 115 results in one or more improvements including butnot limited to: creation of a strain relief such as when shaft 110 is intension (versus securing with a anchoring band which may create anundesired failure point during tensile loading); an increase in torqueresponse of the distal portion of shaft 110; reduced “whipping”(undesired rotations or other undesired movement of a distal portion ofa catheter while the proximal end of the catheter is applied with atorsional force); reduced “snaking” (deflection of an undesired, longportion of a catheter shaft, including deflection of the entire shaft);and combinations of these.

Also shown in FIG. 3B is tip electrode 131 and shaft electrodes 121. Inaddition to adhesive applied to the inner diameter of each electrode,and crimping, swaging or otherwise modifying of one or more ends, afillet material, fillet 132 for tip electrode 131 and fillet 122 forshaft electrodes 121 may be included. Fillet material is preferably anadhesive, configured to further secure each electrode as well aseliminate a sharp edge at each electrode end.

Alternatively, the fillet material may be a polymer, such as the Pebaxshaft material, the fillet formed by adding Pebax and/or reflowing Pebaxmaterial with heat.

Referring now to FIGS. 4-4E, another embodiment of an ablation catheteris illustrated. In FIG. 4, a side-view of ablation catheter 100 isshown. The total length L of the catheter shaft can be approximately 105cm±5 cm, for example. Shaft 110 can include a larger diameter proximalsection 110 a and a smaller diameter distal section 110 b, both of whichare preferably braided. Alternative shaft reductions may be employed,such as an tapered transition, or other transitions preferably includinga reduction of approximately 2 Fr. Braiding comprises typically astainless steel flat wire and/or a nylon strand braiding material,although a wide variety of materials and cross-sectional geometries canbe used for braiding. The stainless steel flat wire is typically0.001″×0.003″ type 304 stainless steel, or equivalent. Braidingparameters preferably range from 40 ppi to 80 ppi. In another preferredembodiment, braiding of 80 ppi in the proximal portion of shaft 110transitions to 60 ppi and then 40 ppi in the distal portion, such as tocreate a relatively constant torque transition during rotation.

Ablation catheter 100 can include handle 150 having an electricalconnector, jack 155, which is electrically connected via multiple signalwires (not shown) to shaft electrodes 121 and tip electrode 131. Handle150 can further include knob 151, which is operably attached to one ormore steering wires, also not shown but described in detail throughoutthis application. Rotation of knob 151 can cause deflection of thedistal portion of shaft 110, such as deflections in one to fourdirections, with symmetric and/or asymmetric deflection geometries.Alternative or additional knobs may be included, such as a knob attachedto a control wire which is further attached to a stiffening member, suchas a stiffening member used to change the curve of a distal portion ofshaft 110.

In FIG. 4A, a side view of the distal end of shaft 110 is illustrated(detail A of FIG. 4), including shaft electrodes 121 and tip electrodes131. While the separations between each electrode are shown asrelatively similar, dissimilar separation distances may be employed.While the lengths of shaft electrodes 121 are shown as relativelysimilar, dissimilar electrode lengths may be employed.

In FIG. 4 B, a cross sectional view of shaft 110 is illustrated (crosssection B-B of FIG. 4). Included within shaft 110 is guide plate 116, anelongate plate constructed of an elastic material such as stainlesssteel or Nitinol. Steering wires 115 are also shown, locatedapproximately 180° from each other and fixedly attached or embedded toshaft 110. The axis formed between the centers of each steering wire 115is perpendicular to the longer axis of guide plate 116. In thisconstruction, deflections in the plane of guide plate 116 are resisted(i.e. guide plate 116 has a preferred bending direction due to the highaspect ratio of its width versus height). Guide plate 116 furtherimproves lateral stiffness of shaft 110. Guide plate 116 can be fixedlyattached (e.g. adhesive attachment) within shaft 110 near its distal end(within or near tip electrode 131) and travels proximally 1″ to 8″,preferably 5″ and also preferably to a location more proximal than thetransition between the smaller diameter and larger diameter sections ofthe shaft. Guide plate 116 is preferably not attached to any steeringwire or steering mechanism.

Also shown in FIG. 4B are multiple signal wires 117, shown grouped inmultiple bundles, which transmit energy, such as RF energy, to theablation elements of catheter 100 such as tip electrode 131 and shaftelectrodes 121. Signal wires 117 can also receive signals from one ormore sensors, such as pairs of thermocouples mounted to or integral witheach electrode. Signal wire sizes and function are described in detailthroughout this application, and specifically in reference to FIG. 1. Inone embodiment, tip electrode 131 can be attached to two 36 gauge wiresand shaft electrodes 121 are each attached to a 36 gauge wire and a 40gauge wire. Tip electrode 131 can be configured to deliver up to 45Watts of RF power utilizing the two 36 gauge wires. Shaft electrode 121can be configured to deliver up to 20 watts of RF power, utilizing theone 36 gauge wire.

In FIG. 4C, a side view of a preferred sub-assembly of shaft 110 isillustrated. The distal end of the shaft can be trimmed inmanufacturing, and the tip electrode is attached. The subassembly ofshaft 110 includes shaft proximal section 110 a, preferably Pebax at5533 to 7533 durometer (typically 7533 durometer); and shaft distalsection 110 b, preferably Pebax at 3533 to 4533 durometer (typically3533 durometer), or at least of a material more elastic that thematerial of shaft proximal section 110 a. Shaft proximal section 110 ais fixedly attached (e.g. via thermal bond) to shaft distal portion 110b at staircase joint 112. The subassembly of shaft 110 can include braid118, as has been described hereabove.

In FIG. 4D, side sectional view of detail C of FIG. 4C is illustrated.The distal end of shaft distal section 110 b is constructed of stiffermaterial than the more proximal portion distal section 110 b (e.g., 5533durometer versus 3533 durometer). The majority of the stiffer portion istrimmed in manufacturing, however a small amount remains which is laterfixedly attached to tip electrode 131. The increased durometer providesa more stable platform for an adhesive bond, as well as for a mechanicalengagement such as a crimp or swage. During manufacturing, a metal ring,anchor ring 144 is placed at the junction of the stiffer portion and theless stiff portion of the distal section 110 b of the shaft as shown.Shaft distal section 110 b can include liner 118, such as a Teflonliner, which can be placed such that one or more steering wires, notshown, are sandwiched between liner 118 and shaft 110 b. In a preferredembodiment, liner 118 can travel proximally into shaft proximal section110 a. Anchor ring 118 can apply additional retaining force to preventsteering wire movement. Anchor ring 118 can span across the differingstiffnesses of distal section 110 b.

In FIG. 4E, an end cross sectional view of section D-D of FIG. 4C isillustrated. Section D-D is positioned within staircase joint 112, andindicates a preferred construction where the stiffer shaft proximalsection 110 a occupies 150° to 170° of the diameter of the shaft, andthe more flexible shaft proximal portion 110 b occupies 190° to 210° ofthe diameter. In an alternative embodiment, shaft proximal section 110 aoccupies 150° to 180° of the diameter of the shaft. The eccentric matingof materials in staircase joint 112 can produce asymmetric, stabledeflection geometries. FIG. 4E depicts a laminate construction includingliner 143, braid 118 and shaft proximal section 110 a and shaft distalsection 110 b. Positioned between liner 143 and shaft proximal portion110 a is a first steering wire 115 a, and positioned between liner 143and shaft distal portion 110 b is a second steering wire 115 b. Alsoincluded are signal wires, connecting the ablation elements to a jack ona handle mounted to the proximal end of shaft 110, signal wires,ablation elements, handle and jack not shown but described in detailthroughout this application.

Referring now to FIGS. 5A, 5B and 5C, side views of the end of ablationcatheter 100 of FIG. 4 are illustrated. In FIG. 5A, two deflections ofthe distal end of shaft 110 are shown, depicting typical asymmetricdeflections (i.e. larger radius of curvature when deflecting toward theleft side of the page). For example, the distal end of the shaft mayhave a radius of curvature of approximately 0.85″ when deflected in onedirection (e.g., as illustrated on the left side of FIG. 5A) and mayhave a radius of curvature of approximately 0.60″ when deflected in theopposite direction (e.g., as illustrated on the right side of FIG. 5A).Additionally, the differing radii of curvature may cause the shaft todeflect at different points along the shaft. For example, as shown inFIG. 5A, when deflecting with a larger radius of curvature, the shaft isdeflected at a point more proximal to the point of deflection when theshaft is deflected with a smaller radius of curvature. The distancebetween deflection points can be approximately 0.75″, for example.Numerous asymmetric deflection configurations, as are describedthroughout this application, can be employed to cause this asymmetry.The staircase joint 112 of FIG. 3A and FIG. 4C, the inclusion of a guideplate such as the guide plate of FIG. 4B, the addition of a stiffeningmember in or near shaft 110 (as is described in reference to FIG. 10herebelow), non-uniform braiding patterns, and other eccentricconstructions may individually, or in combination, create asymmetrybetween two or more deflection directions.

FIGS. 5B and 5C include side view and cross sectional views of shaft 110near the deflection point of the shaft. The shaft 110 can include aguide plate 116, configured to limit motion in a plane and/or createasymmetric deflection. FIG. 5B includes an end sectional view and a sideview, each showing deflection amounts. In FIG. 5B, the plane of guideplate 116 can be perpendicular to the deflection directions, anddeflection is only marginally resisted (by the relatively low stiffnessof guide plate 116). In FIG. 5C, the plane of guide plate 116 can beparallel to the deflection directions, and deflection is met with a verylarge force, limiting the magnitude of the deflection. In alternativeembodiments, guide plate 116 can be at an angle between perpendicularand parallel to the deflection direction, creating more complexgeometries of deflection (e.g. 3-D geometries). In another alternativeembodiment, the guide plate length is selected to determine the geometryof deflection.

Referring now to FIG. 6, an exploded view of a preferred construction ofhandle 150 of catheter 100 is illustrated. Handle 150 can includemultiple controls, such as knobs or buttons which can manipulate thegeometry of the catheter (e.g. via steering wires and the symmetric andasymmetric deflection mechanisms described above), activate a functionalelement mounted to the catheter shaft or tip (e.g. an ablation elementconsisting of a platinum electrode), and permit, cause, activate orde-activate other functions. Handle 150 can be fixedly attached to shaft110, which includes distal tip electrode 131 and shaft electrodes 121.Ablation catheter 100 can also include a capture device 300 which can beplaced at the junction between handle 150 and shaft 110 and be slidablyreceived by shaft 110. When removably attached to handle 150, capturedevice 300 can act as a strain relief for shaft 110. Alternatively oradditionally, capture device 300 can be slidably moved toward the distalend of catheter 100, engage the proximal side of the distal end andcapture the distal end within capture device 300, allowing protectedinsertion of the distal end of catheter 100 into a percutaneousintroducer.

Handle 150 can include a tensioning mechanism such that the forcerequired to perform a deflection can be adjusted and/or a specificdeflection geometry can be maintained.

Handle 150 can include the following components as shown: bottom housing51, preferably of polycarbonate construction; cam 52, preferably ofpolycarbonate construction; screw 53, preferably of stainless steelconstruction and configured to adjust a steering parameter; hypotubecoupling 54 preferably of stainless steel construction; PC Boardassembly 55 configured to perform one or more switching or otherfunctions; connector sleeve 56, connector 57 configured to electricallyattach one or more components of ablation catheter 100 to a separatedevice such as an RF generator or an ECG monitor; top housing 58preferably of polycarbonate construction; O-Ring 59 preferably of n-bunarubber construction; steering knob 60 preferably of polycarbonateconstruction; tension adjust knob 61 preferably of polycarbonateconstruction; tension adjust screw 62; dowel pins 63; tension controlknob 64; and handle overmold grip 65.

Referring now to FIGS. 7A and 7B, which illustrate end and sidesectional views, respectively, of a preferred construction of a shaftelectrode. Shaft electrode 121 is preferably manufactured of platinum orplatinum-iridium and configured to deliver unipolar or bipolar RFenergy. Shaft electrode 121 can include a wall 136, shown at uniformthickness but alternatively of varied thickness. Preferred dimensionsare an inner diameter of 0.093″ to 0.095″, a wall thickness of 0.006″ to0.010″, and a length of 1 to 8 mm, more preferably a length of 2 mm. Ina preferred embodiment, the ratio of the outer diameter of shaftelectrode 121 to the inner diameter of the shaft electrode is in therange of 1.09:1 to 1.11:1, and more specifically a ratio ofapproximately 1.10:1. Inner diameter to outer diameter ratios in thisrange have been shown to produce superior lesions such as lesionscreated which block aberrant electrical signals but significantly limitthe possibility of tissue charring or coagulum formation.

Shaft electrode 121 can include two thermocouples 138 a and 138 b,although a single thermocouple or three or more thermocouples could beincorporated. Thermocouples 138 a and 138 b can be located approximately180° from each other on the inner diameter of shaft electrode 121.Thermocouples 138 a and 138 b can be placed at the approximate midpointof (the length of) shaft electrode 121, although other locations can beused such as the proximal and/or distal ends of the electrode.Additional thermocouples may be incorporated creating symmetric orasymmetric thermocouple positioning geometries. When manufactured intoan ablation catheter of the present invention, shaft electrode 121 aswell as thermocouples 138 a and 138 b can be electrically attached tosignal wires which travel proximally to a handle of the device, as hasbeen described in detail above.

Referring now to FIGS. 7C and 7D, which illustrate end and sidesectional views, respectively, of a preferred construction of a tipelectrode. Tip electrode 131 is preferably manufactured of platinum orplatinum-iridium and configured to deliver unipolar and/or bipolar RFenergy. Tip electrode 131 can include a rounded, or otherwise atraumaticdistal end. Tip electrode 131 can also include a wall 137, shown atuniform thickness but alternatively of varied thickness, such as athicker wall in the rounded tip area. Preferred dimensions are an innerdiameter of 0.093″ to 0.095″, a wall thickness of 0.006″ to 0.010″, anda length of 1 to 8 mm, more preferably a length of 4 mm. In a preferredembodiment, in the straight portion of tip electrode 131, the ratio ofthe outer diameter to the inner diameter is in the range of 1.09:1 to1.11:1, and more specifically a ratio of approximately 1.10:1 Innerdiameter to outer diameter ratios in this range have been shown toproduce superior lesions such as lesions created which block aberrantelectrical signals but significantly limit the possibility of tissuecharring or coagulum formation.

Tip electrode 131 can include two thermocouples 139 a and 139 b,although a single thermocouple or three or more thermocouples could beincorporated. Thermocouples 139 a and 139 b can be located approximately180° from each other on the inner diameter of tip electrode 131.Thermocouples 139 a and 139 b are placed at the approximate midpoint ofthe tip electrode 131, although other locations can be used, such ascloser to the distal end of tip electrode 131. Additional thermocouplesmay be incorporated creating symmetric or asymmetric thermocouplepositioning geometries. When manufactured into an ablation catheter ofthe present invention, tip electrode 131 as well as thermocouples 139 aand 139 b can be electrically attached to signal wires which travelproximally to a handle of the device, as has been described in detailabove.

Referring now to FIG. 7E, a side sectional view of a preferredconstruction of the distal portion of a shaft of an ablation catheter ofthe present invention is illustrated. The distal portion of shaft 110can include at its distal end, tip electrode 131 which can be adhesivelymounted to the distal end of shaft 110. In one embodiment, the proximalend of tip electrode 131 can also be crimped or swaged onto shaft 110,and an adhesive fillet 132 can be incorporated, both described in detailabove. Shaft 110 can further include guide plate 116, preferably a flatstainless steel plate, with a high ratio of width to thickness and alength that can traverse proximally to a point where shaft 110 changesfrom a first diameter to a larger second diameter (e.g. approximately 5inches in length). Guide plate 116 can resist bending in certaindirections, as has been described above. A restoring, or straighteningforce can also be provided by guide plate 116, such that when adeflecting force is removed, guide plate 116 and shaft 110 straighten.In an additional or alternative embodiment, guide plate 116 may have avariable thickness, such as a greater thickness at its distal end thanits proximal end, or a greater thickness at its proximal end than itsdistal end. In one embodiment, one end has a thickness of 0.005″ and theother end has a thickness of 0.002″. Shaft 110 can include multipleshaft electrodes 131, in a band construction (reference FIGS. 7A and 7B)and adhesively mounted to shaft 110. Adhesive fillets 122 can beincluded to create a smooth edge and increase the attachment force ofshaft electrodes 121. Shaft 110 can further include braid 118 andsteering wires 116, as has been described in detail above.

Referring now to FIGS. 8A and 8B, an alternative construction of a shaftelectrode of the present invention is illustrated. FIG. 8A depicts shaftelectrode 123 in an assembled configuration of an ablation catheter, andFIG. 8B shows an exploded view of the construction of FIG. 8A. Shaftelectrode 123 can include a reduced diameter flange on each end, sizedto approximate the inner diameter of proximal section 110 a and distalsection 110 b. Shaft electrode 123 can include a middle portion with adiameter approximating the outer diameter of shaft 110, preferably aslightly larger diameter (e.g. a diameter 0.001″-0.050″ larger,preferably approximately 0.004″ larger). Shaft electrode 123 can includeone or more thermocouples mounted to its inner surface, not shown butmore preferably two thermocouples positioned approximately 180° fromeach other on the inner diameter of shaft electrode 123. Signal wires117 pass through a lumen of the shaft and attach to shaft electrode 123.One or more signal wires 117 may pass through a lumen of shaft electrode123 (lumen not shown), travel distally through a lumen of the shaft, andterminate with a connection to tip electrode 131, which is fixedlyattached to the distal end of the shaft. Shaft electrode 123 and tipelectrode 131 can be configured to provide ablation energy, recordelectrical and temperature signals, and perform other functions as hasbeen described above in reference to the ablation elements of thepresent invention.

Referring now to FIGS. 9A through 9O, numerous configurations ofablation elements, particularly shaft electrodes and tip electrodes, ofthe ablation catheters of the present invention are illustrated. Theelectrodes may be configured in symmetric or asymmetric geometries. Theelectrodes may have smooth surfaces on their inner diameter and/or outerdiameter, or may include surface modifications such as bumps, ridges,dimples or grooves (such as to increase surface area or modify bloodflow), and may include projections such as heat dissipating fins. Theelectrodes may have relatively uniform wall thicknesses, or the wallsmay have varied thicknesses such as tapered or stepped profiles. Each ofthe electrodes is preferably configured to be attached to multiplethermocouples configured to provide redundant temperature informationfor one or more energy delivery algorithms. Each of the electrodes ispreferably made of platinum or platinum-iridium, although any materialthat can transmit RF energy to tissue can be used. In addition toproviding ablative RF energy, each of the ablation elements of thepresent invention can preferably provide the function of recordingelectrical signals found in tissue, such as ECG signals.

Referring specifically to FIG. 9A, a perspective view of two helicallyshaped shaft electrodes is shown. Electrodes 121 e′ and 121 e″ areconfigured to be mounted to a shaft of an ablation catheter of thepresent invention, such as in a flush or raised mounting scheme. Thelarge surface area of electrodes 121 e′ and 121 e″ can provide anenhanced cooling effect. While either electrode could be used singly,use of both electrodes positioned as shown in FIG. 9A would support bothunipolar and bipolar (between electrode 121 e′ and 121 e″ or to aseparate electrode) RF energy delivery. In addition, electrodes 121 e′and 121 e″ could record bipolar electro grams.

Referring specifically to FIG. 9B, a perspective view of two partialband shaft electrodes 121 f are shown mounted to shaft 110. The partialband construction of electrodes 121 f may be configured to provideenhanced cooling (e.g. internal cooling), promote directional bending,and provide other benefits. Electrodes 121 f may deliver unipolar orbipolar energy, such as bipolar energy between neighboring electrodes,or between any pair of electrodes. In an alternative or additionalembodiment, electrodes 121 f can be configured to create asymmetricsteering of the distal portion of shaft 110.

Referring specifically to FIG. 9C, a perspective view of tip electrode131 e is shown with a square tip, and flattened sides.

Referring specifically to FIG. 9D, a perspective view of three “S”shaped band electrodes 121 g are shown. The “S” geometry providesenhanced cooling of the electrode due to the large, separated surfaceareas. Also shown in FIG. 9D is a perspective view of tip electrode 131f that has a rounded tip, but flattened sides.

Referring specifically to FIG. 9E, a side view of shaft electrode 121 fis shown. Shaft electrode 121 f includes a variable wall thickness,where one end of shaft electrode 121 f has a thicker wall than the otherend, and a relatively linear taper exists between one end and the other.

Referring specifically to FIG. 9F, a side view of shaft electrode 121 gis shown. Shaft electrode 121 g includes a variable wall thickness,where each end has a thinner wall than a midpoint location, and arelatively linear taper exists between the midpoint and each end. Theouter diameter of shaft electrode 121 g is in a relatively constantdiameter, while the inner diameter varies to accommodate the increasedwall thickness. Alternatively, a similar asymmetric profile isincorporated into a tip electrode of the present invention.

Referring specifically to FIG. 9G, a side view of tip electrode 131 h isshown. Tip electrode 131 h includes a variable wall thickness, where thewall is thicker at the distal tip, tapering relatively linearly to theproximal end.

Referring specifically to FIG. 9H, a side view of tip electrode 131 i isshown. Tip electrode 131 i includes a variable wall thickness, where thewall is thicker at the proximal end, tapering relatively linearly to thedistal tip.

Referring specifically to FIGS. 9J and 9K, side and end views,respectively, of tip electrode 131 j are shown. Tip electrode 131 jincludes a variable wall thickness, where the cross sectional profileincludes a thicker wall on one side than the other. Alternatively, asimilar asymmetric profile is incorporated into a shaft electrode of thepresent invention. The orientation of the asymmetric electrode at thetip or on the shaft may be such that the thicker portion is configuredto contact tissue during ablation, such as by being on the outside of adeflecting curve. The thicker and thinner portions can be configured tooptimize transfer of heat to circulating blood.

Referring specifically to FIG. 9L, an end view of shaft electrode 121 kis shown. Shaft electrode 121 k includes a projecting fin 125, orientedradially in toward the center axis of shaft electrode 121 k. Projectingfin 125 is configured to provide a heat sink, improving the coolingproperties of shaft electrode 121 k. Alternatively, a similar projectingfin is incorporated into a tip electrode of the present invention.

Referring specifically to FIG. 9M, an end view of shaft electrode 121 mis shown. Shaft electrode 121 m includes one or more projecting fins125, projecting radially out from the center axis of shaft electrode 121m. Projecting fins 125 are configured to provide a heat sink, residingin the blood flow and improving the cooling properties of shaftelectrode 121 m. In a preferred embodiment, shaft electrode 121 mincludes a tissue contacting portion without projecting fins, (e.g. onthe outside of a deflecting curve geometry), and fins 125 are positionedaway from the tissue contacting portion (i.e. the fins 125 are in theflow of blood or otherwise away from the tissue to be ablated).Alternatively, similar one or more outwardly projecting fins areincorporated into a tip electrode of the present invention.

Referring specifically to FIGS. 9N and 9P, a side and end view,respectively, of shaft electrode 121 n is shown. Shaft electrode 121 nincludes a variable wall thickness, where each end has a thinner wallthan a midpoint location, and a relatively linear taper exists betweenthe midpoint and each end. The inner diameter of shaft electrode 121 gis in a relatively constant diameter, while the outer diameter varies toaccommodate the increased wall thickness. Alternatively, a similarasymmetric profile is incorporated into a tip electrode of the presentinvention.

The ablation elements of the present invention may incorporate theconstruction features illustrated and described in reference to FIGS. 9Athrough 9P, singly or in combination. While the varied wall thicknessesof these ablation elements have been accomplished with relatively lineartapers, non-linear variations could be employed. Other variations ofnonconstant wall thickness, surface modifications such as bumps,dimples, ridges and grooves, and other asymmetries may be incorporated,singly or in combination, and remain within the spirit and scope of thisapplication.

Referring now to FIG. 10, a side view of a distal end of an ablationcatheter 100 of the present invention is illustrated. Ablation catheter100 includes a shaft 110 which includes tip electrode 131 mounted on thedistal end of shaft 110, and shaft electrodes 121 mounted to shaft 110,proximal to tip electrode 131. Within the outer diameter of shaft 110 ismalleable member 111, such as a plastically deformable wire or band thatcan be embedded in the wall of shaft 110. Alternatively, malleablemember 111 may be maintained in contact with shaft 110 by being capturedbetween shaft 110 and an inner tube such as a liner, or via fasteningmeans such as an adhesive. Malleable member 111 can be configured to beplastically deformed, either by pressing the distal portion of the shaftagainst tissue, hand manipulation by an operator, and/or by an internalsteering mechanism. Malleable member can also be configured to maintaina desired shape, until a restoring force is applied, such as via asteering wire or other steering mechanism, or a straightening force suchas a force generated by hydraulics or pneumatics delivered to a distalportion of the shaft 110 via a fluid transfer lumen, not shown. In analternative embodiment, member 111 is resiliently elastic, such as toresist bending in a first direction (similar to the guide platesdescribed hereabove), or to provide a restoring force which straightensthe distal portion of the shaft when no other force is being applied.

Referring now to FIGS. 11A and 11B, a side view of a distal portion ofan ablation catheter of the present invention is illustrated. In FIG.11A, the distal portion is shown in an unexpanded state, and in FIG. 11Bthe distal portion is shown in an expanded state. The distal end ofshaft 110 can include multiple shaft electrodes 121, of a similarconstruction to the shaft electrodes described throughout thisapplication. For example, the distal end of shaft 110 can be split, andballoon 141 can be mounted between the split ends. Balloon 141 can befluidly connected to a pressure source, such as a saline source or otherfluid source, such as a source activated by a control on a handle of theablation catheter (fluid source and handle not shown). The ablationcatheter of FIGS. 11A and 11B can also be configured to deliver unipolaror bipolar energy, such as bipolar energy delivered between two“parallel” electrodes 121, or any pair of electrodes. Balloon 141 may bea compliant balloon, such that increased inflation pressure continuallyincreases the separation distance of the split end of shaft 110, orballoon 141 may be a non-compliant balloon, such that increasedinflation pressure results in minimal increase in the separationdistance beyond a fixed distance. Balloon 141 may have an inflatedgeometry that is relatively parallel and linear as shown in FIG. 11B, ormay be configured to create a non-parallel, curved or otherwisenon-linear geometry. Balloon 141 may be configured to additionallyprovide a cooling function, such as a balloon which receives acontinuous replacing volume of cool saline, prior to, during and/orafter delivery of ablation energy.

Referring now to FIGS. 12A and 12B, a side view of a distal portion ofan ablation catheter of the present invention is illustrated. In FIG.12A, the distal portion is shown in an undeployed state, and in FIG. 12Bthe distal portion is shown in a deployed, “open V” geometry. Shaft 110includes expandable carrier assembly 142 comprising two tip electrodes131 a and 131 b. The two tip electrodes 131 a and 131 b may beelectrically isolated from each other (e.g. via an insulator located onone or both mating surfaces), or may conduct electricity between the twowhen in the undeployed condition of FIG. 12A. Unipolar and bipolarenergy can be delivered in both the deployed and undeployed states.Advancement of a control shaft, not shown but preferably operablyconnected to a control on a handle of the ablation catheter, causeselectrodes 131 a and 131 b to assume the “open V” geometry. Shaft 110can further include one or more shaft electrodes 121, such that bipolarenergy can be delivered between electrodes 131 a and/or 131 b and shaftelectrode 121. Alternatively or additionally, shaft electrode 121 maydeliver unipolar energy. In a preferred method, carrier assembly 142 isdeployed as shown in FIG. 12B, and shaft 110 is advanced such thattissue is positioned between electrodes 131 a and 131 b. Unipolar energycan be delivered from either or both electrodes 131 a and 131 b, andbipolar energy can be delivered between electrodes 131 a and 131 b.

Referring now to FIGS. 13 and 14, a side sectional view of a distalportion of an ablation catheter of the present invention is illustrated.Shaft 110 can include a tapered profile transitioning from a largerdiameter section, through tapered joint 113, to a smaller diametersection having a steerable portion, as has been described in detailabove in reference to various embodiments of the present invention.Shaft 110 may include symmetric or asymmetric steering, also describedin detail hereabove in reference to various embodiments of the presentinvention. Steering wires 115 can be “free floating” in the largerdiameter portion of shaft 110, and frictionally attached to shaft 110 inthe smaller diameter portion, such as a frictional engagement caused byembedded steering wires 115 in the wall of the smaller diameter portion,or sandwiching steering wires 115 between a liner and the inner wall ofshaft 110. Steering wires 115 are operably attached to one or morecontrols, such as a rotating knob on the handle of the catheter, handleand controls not shown but described in detail above.

At the distal end of shaft 110 is tip electrode 131, preferablyadhesively mounted to shaft 110 as well as crimped or swaged on itsproximal end. Attached to an inside wall of tip electrode 131 is asignal wire 117 a and thermocouple 139. Proximal to tip electrode 131 isat least one shaft electrode 121, preferably attached to shaft 110 withadhesive, and in a preferred embodiment, further attached by crimpingone or both ends of shaft electrode 121. Signal wires 117 b can passthrough a hole (e.g. a laser cut hole) in the wall of shaft 110 (as wellas through any liners, braids, or other internal structures). Attachedto an inside wall of shaft electrode 121 is a signal wire 117 b andthermocouple 138.

Referring now to FIGS. 15, 15A, 15B, 15C, 15D, 15E and 15F, an ablationcatheter of the present invention is illustrated, where an advanceablecarrier assembly can be deployed from the catheter's distal end.Referring to FIG. 15, ablation catheter 100 includes a handle 150 on theproximal end of shaft 110. Handle 150 includes trigger grip 154configured to provide an ergonomic holding surface for an operator ofablation catheter 100. Also included in handle 150 is jack 155,electrically connected to one or more ablation elements of catheter 100such as shaft electrodes 120. On the distal end of shaft 110 is adeployable carrier assembly, distal ablation assembly 130, which isoperably attached to knob 151 of handle 150. Ablation catheter 100further includes capture device 300, removably engaged with handle 150and configured to provide a strain relief between the proximal end ofshaft 110 and handle 150, as well as perform a capture function forintroducing the distal end of ablation catheter 100 into a percutaneoussheath, such as a sheath placed in the femoral vein of a patient.

Referring now to FIG. 15A, distal ablation assembly 130, shown in itsdeployed state, is attached to control shaft 119, which is operablyattached to knob 151 of handle 150. Signal wires 117 are attached to oneor more ablation elements of distal ablation assembly 130 as well asshaft electrodes 121. Shaft electrodes 121 are adhesively otherotherwise attached to shaft 110, and include fillets 122 at either end.Within a lumen of shaft 110 is tube 127, which surrounds signal wires117 such as to protect signal wires 117 from damage. On the proximal endof shaft 110 is strain relief 126, preferably heat shrink tubingsurrounding shaft 110. Steering wires 115 travel within the OD of shaft110 such as to facilitate symmetric or asymmetric steering of the distalportion of shaft 110.

Referring now to FIGS. 15B, 15C and 15D, the distal end of shaft 1110 isshown. In FIG. 15B, a side view of the distal end of shaft 110 is shownwith distal ablation assembly 130 in its undeployed state. In FIG. 15C,a side view of the distal end of shat 110 is shown with distal ablationassembly 130 in its deployed state. Distal ablation assembly 130includes four carrier arms 133, each of which includes a distalelectrode 131. Alternatively, the distal ablation assembly can compriseonly two carrier arms which overlap to form the assembly shown in FIG.15D. Unipolar or bipolar RF energy can be transmitted to tissue byanyone of distal electrodes 131 and/or shaft electrodes 121. Bipolarenergy can be transmitted between any pair of distal electrodes 131and/or shaft electrodes 121. FIG. 15D illustrates an end view of thedeployed condition of FIG. 15C.

Referring now to FIGS. 15E and 15F, a preferred shape of distalelectrodes 131 is illustrated. The pie shape provides for an efficient,compacted or reduced volume (i.e. minimal open space between components)when distal ablation assembly 130 is in the undeployed condition of FIG.15B. As shown in FIGS. 15E and 15F, a through-hole may be included inelectrode 131 such as to pass carrier arm 133 through, and/or to passone or more signal wires through.

Referring now to FIG. 16, an ablation catheter of the present inventionis illustrated, where an advanceable carrier assembly can be deployedfrom the distal end. Shaft 110 surrounds control shaft 119 which can beadvanced and retracted, such as a retraction which causes distalablation assembly 130 to be contained within the lumen of shaft 110, andan advancement which causes distal ablation assembly 130 to exit thedistal end of shaft 110, expanding to a fork shaped condition. Distalablation assembly 130 can include two carrier arms 133, and at the endof each carrier arm is distal electrode 131 a and 131 b. Distal ablationassembly 130 can be partially deployed, as shown in FIG. 16, such thatthe two carrier arms 133 have a reduced (more acute) angle as comparedto the condition where control shaft 119 is further advanced. Slightadvancements and retractions of control shaft 119 cause the anglebetween the two carrier arms to increase and decrease respectively. In apreferred method, control shaft 119 is advanced to cause a sufficientangle to surround a portion of tissue, and subsequent retraction causescarrier arms 133 and electrodes 131 a and 131 b to “pinch” or otherwisecapture the targeted tissue. In the pinched state, unipolar and/orbipolar (between electrodes 131 a and 131 b) can be delivered to createa precision lesion in the tissue. A steering mechanism, such as asymmetric or asymmetric steering mechanism may be included. In apreferred embodiment, at least one thermocouple is included in eachelectrode 13 a and 131 b. Although distal ablation assembly 130 is shownwith two carrier arms 133, alternative embodiments include three or morecarrier arms 133.

Referring now to FIGS. 17A, 17B and 17C, the distal portion of anablation catheter of the present invention is illustrated including anadvanceable carrier assembly deployable from the distal end. Shaft 110can surround control shaft 119 which can be advanced and retracted, suchas a retraction which causes shaft ablation assembly 120 to be containedwithin a lumen of shaft 110, and an advancement which causes shaftablation assembly 120 to exit the distal end of shaft 110, and expand tothe geometry shown in FIG. 17C. Shaft ablation assembly 120 includesfour carrier arms 133 upon which at least one electrode 121 is fixedlyattached (two electrodes 121 on each carrier arm shown). Electrodes 121preferably have a pie or wedge shape to allow efficient volumecompression when in the undeployed state. At the end of the four carrierarms 133 is tip electrode 131.

FIG. 17A shows the control shaft fully retracted, shaft ablationassembly contained within a lumen of shaft 110, and tip electrode 131located at the distal end of shaft 131. In this configuration, energycan be delivered from tip electrode 131 (e.g. unipolar RF energy). FIG.17B shows the control shaft partially or fully advanced, prior toexpansion of carrier arms 133 and shaft ablation assembly 120. FIG. 17Cshows the control shaft in the fully advanced condition, with carrierarms 133 and shaft ablation assembly 120 fully expanded. Unipolar orbipolar energy can be delivered by and between distal electrode 131 andelectrodes 121 (e.g. bipolar RF energy between any electrode pair). Theablation catheter of FIGS. 17A, 17B and 17C include signal wires, notshown, but electrically connected to tip electrode 131 and electrodes121. A steering mechanism, such as a symmetric or asymmetric steeringmechanism may be included. In a preferred embodiment, at least onethermocouple is included in each electrode 121. In another preferredembodiment, at least two thermocouples are included in tip electrode131. Although shaft ablation assembly 120 is shown with four carrierarms 133, alternative embodiments include two, three, or more than fourcarrier arms 133.

Referring now to FIGS. 18A, 18B, 18C and 18D, an ablation catheter ofthe present invention is illustrated, where a carrier assembly can betransitioned from a near linear state, to an expanded state. In thelinear state, two carrier arms 133 are relatively linear and parallel toone another, and reside at a location distal to the distal end of shaft110. A control shaft 119 can reside between the two carrier arms 133,and includes tip electrode 131 at its distal end. The proximal end ofcontrol shaft 119 can be operably attached to a control on a handle ofthe ablation catheter (handle and control not shown but described indetail hereabove). Retraction of control shaft 119 can cause the twocarrier arms 133 to bow radially outward as shown in FIG. 18D.Advancement of control shaft 119 can cause the two carrier arms 133 totransition to the near linear state shown in FIG. 18A.

Mounted to the two carrier arms 133 are electrodes 121, preferably shownin the staggered configuration shown in FIG. 18A, such as to allowcompact volume when carrier arms 133 are in the linear state. Electrodes121 are configured in the partial band construction shown in FIGS. 18Band 18C. Energy can be deployed in the linear or expanded conditions.

Referring now to FIGS. 19A, 19B, 19C, 19D and 19E, an ablation catheterof the present invention is illustrated, where a carrier assembly can betransitioned from a near linear state, to an expanded state. In thelinear state, two carrier arms 133 are relatively linear and parallel toone another, and each consist of approximately one-half of shaft 110′which has been slit at a location near the distal end, the slit 1000traveling proximally such as to create the desired deployed geometry(e.g. desired deployed diameter). A control shaft 119 resides betweenthe two carrier arms 133, and includes tip electrode 131 at its distalend. The proximal end of control shaft 119 is operably attached to acontrol on a handle of the ablation catheter (handle and control notshown but described in detail hereabove). Retraction of control shaft119 causes the mid portions of the two carrier arms 133 to bow radiallyoutward as shown in FIG. 19E. Advancement of control shaft 119 causesthe two carrier arms 133 to transition to the near linear state shown inFIG. 19D.

Mounted to the two carrier arms 133 are electrodes 121, shown in thestaggered configuration of FIG. 19D, but alternatively one or moreelectrodes 121 may be adjacent the other. Electrodes 121 are configuredin the half band construction shown in FIG. 18C. Tip electrode 131 isshown in the reduced proximal flange, rounded distal tip constructionshown in FIG. 19B. FIG. 19A shows shaft 110′ with a slit 1000 allowingexpansion of carrier arms 133. FIG. 19A shows electrodes 131 and 121removed, and the lumen (for insertion of tip electrode 131) and recesses128 (for attachment of shaft electrodes 121). Energy can be deployed inthe linear or expanded conditions.

Referring now to FIGS. 20A, and 20B, an ablation catheter of the presentinvention is illustrated including a carrier assembly configured to betransitioned from a compact spiral state to an expanded spiral state.Carrier arm 133 can include tip electrode 131 at its distal end, and afilament electrode 129 along a majority of its length. In the compactstate shown in FIG. 20A, carrier arm 133 is shown in a tight spiral.Advancement or retraction of one or more control shafts, not shown,causes the spiral to unfurl as shown in FIG. 20B. Also as shown in FIG.20B, carrier arms 133 may deflect such as to assume the candy-canegeometry depicted. Energy can be delivered in the compact or expandedstate, and can be delivered from either or both the tip electrode 131and filament electrode 129, in either unipolar or bipolar mode.

Referring now to FIGS. 21A, and 21B, an ablation catheter of the presentinvention is illustrated including a carrier assembly configured totransition from a compact spiral state to an expanded spiral state.Carrier arm 133 can include tip electrode 131 at its distal end, and twoor more discrete electrodes 121 along its length. In the partiallyexpanded shown in FIG. 20A, carrier arm 133 is unfurled from a compactstate, not shown. Advancement or retraction of control shaft 119 cancause the spiral to expand and contract. The distal end of the ablationcatheter may also deflect, as shown in FIG. 21B, to assume thecandy-cane geometry depicted. Energy can be delivered in the compact orexpanded state, and can be delivered from any of the tip electrode 131and discrete electrodes 121, in either unipolar or bipolar mode.

Referring now to FIGS. 22A, and 22B, an asymmetrically bending shaft ofthe present invention is illustrated. Shaft 110 includes multiple wedges134 along its length. Wedges 134 may be pie shaped, as shown in FIG.22B, cube shaped, or configured in another geometry. In a preferredembodiment, wedges 134 are constructed of a softer material than thematerial of shaft 110, such that deflection toward the base of eachtriangle wedge 134 is a smaller radius than deflection toward the peakof each triangle, as shown in FIG. 22B. Shaft 110 may include multiplelevels of stiffness along its length, e.g. by materials of two differentdurometers. In a preferred configuration, a proximal section of theshaft is stiffer than a distal section of the shaft, and the distalsection of the shaft is stiffer than the wedges 134.

Referring now to FIGS. 23A, 23B and 23C, an asymmetrically bending shaftof the present invention is illustrated. Shaft 110 includes multiplewedges 134 a and 134 b along its length. Wedges 134 a and 134 b includedifferent geometries such as to cause a complex deflection pattern whena deflection force is applied to the portion of shaft 110 includingwedges 134 a and 134 b. In the embodiment depicted in FIG. 23A, wedge134 a has a symmetric, rectangular profile and wedge 134 b has aneccentric, partial spherical geometry. Combinations of wedge 134 a and134 b can be used to create one or more complex deflection geometries,including both symmetric and asymmetric deflection geometries as havebeen described above. In a preferred embodiment, a deflection in a firstdirection results in a small radius of curvature, as shown in FIG. 23B,and a deflection in the opposite direction results in a larger radius ofcurvature, as shown in FIG. 24C. In a preferred embodiment, wedges 134 aand 134 b are less rigid (have softer durometers) than the portion ofshaft 110 proximate each wedge, such as to create a symmetric orasymmetric hinge. In an alternative embodiment, wedges 134 a and/or 134b are stiffer than the neighboring shaft 110 material, and a hinge iscreated in the shaft 110 portion between two wedges. Wedges 134 a and/or134 b may be constructed and positioned such as to create a preferreddeflection direction, such as to avoid bending in an undesireddirection.

Referring now to FIG. 24, an asymmetrically bending shaft 110 of thepresent invention is illustrated. FIG. 24 depicts a method for steeringthe distal end of the catheter and maintaining the planarity of thedistal portion during operator induced deflection (when being steered).Shaft 110 includes multiple slits, 135 a and 135 b along its length.Slits 135 a can be positioned along one side of shaft 110, and slits 135b can be on the opposite side of shaft 110 (e.g. approximately 180°apart). Slits 135 b can be of larger width than slits 135 a, such thatthe bending force required to curve toward the side that slits 135 b arepositioned is less than the bending force required to curve toward theside that slits 135 a. In the configuration shown, the radius formed incurving toward the side that slits 135 b are positioned, will be smallerthan the radius formed in curving toward the side that slits 135 a arepositioned (e.g. asymmetric deflection at similar deflection force).Slits 135 a and slits 135 b further provide preferential bending, inother words bending in the two directions aligned toward the sides thateither slits are positioned is preferred versus bending in a differentdirection. The segments of shaft 110 that are stiffer (e.g. not cut) actas a spine keeping the bending in a single plane. In addition, the slitson one side of this steering mechanism can be different in geometry(e.g. size) from the slits on the opposite side. By making the slits oneach side different, the distal portion of shaft 110 can deflect withtwo different sized curves (e.g. curve formed by bending in a firstdirection, and curve formed by bending in a direction 180° from thefirst direction). Shaft 110 or FIG. 24 may be covered by an outer tube,such as a liner, to avoid sharp edges on the outer diameter of theablation catheter. Alternatively or additionally, slits 135 a and/orslits 135 b may be filled with a material, such as a material softerthan the material of shaft 110.

Referring now to FIG. 25, a preferred embodiment of a percutaneoustreatment and/or diagnostic catheter of the present invention isillustrated. Catheter 200 can include flexible shaft 210. Handle 250 canbe located on the proximal end the shaft and can include multiplecontrols, such as knob 251 and button 252. Button 252 can be configuredto initiate and/or discontinue one or more functions of catheter 200.Knob 251 can be configured, when rotated, to cause distal portion of theshaft to deflect in one or more directions, such as to curve in onedirection when rotated clockwise, and another direction when rotatedcounter-clockwise. In a preferred embodiment, described in detail above,knob 251 can be attached to two steering wires which are captured in thedistal portion of the shaft and cause bi-directional steering such assymmetric or asymmetric steering, also described in numerous embodimentsabove. In alternative embodiments, 1, 3, 4 or more steering wires may beincorporated, such as steering wires separated by approximately 120° or90°, causing deflection in a single plane, or two or more planes. Eachdeflection may have a simple geometry such as a single plane, fixedradius curve, or more complex geometries such as bending in 3-D space.

Additional controls may be integrated into handle 250 to performadditional functions. A connector, not shown, can be integral to handle150 to allow electrical, mechanical (e.g. mechanical linkage or fluidinjection) or other connections from ablation catheter 100 to one ormore other medical or other devices.

The shaft can also include multiple shaft functional elements 221 a, 221b, 221 c and 221 d. The shaft can further include tip functional element231, such as an atraumatic (e.g. rounded tip), functional element. In analternative embodiment, tip functional element 231 may include multiplefunctional elements.

In a preferred embodiment, the functional elements of catheter 200 canbe attached to conduits such as signal wires, fluid delivery tubes,optical fibers or other conduits, not shown but traveling within shaft210 and connecting to a mechanism within handle 250 and/or a connectoron handle 250.

Functional elements of catheter 200 can include but are not limited tosensors; transducers and combinations thereof. Transducers include butare not limited to: electrodes such as platinum electrodes configured todeliver energy and receive electro grams; sound transducers such asultrasonic, acoustic and subsonic transducers; drug delivery elements;radiation sources, magnetic sources; heat generators; cooling orcryogenic transducers such as a cooling element connected to a conduitthrough which cooling liquid passes near an ablation element; othertransducers and combinations thereof. Sensors include but are notlimited to: temperature sensors such as thermocouples; blood sensorssuch as blood gas sensors or blood glucose sensors; respiration sensors;fluid flow sensors such as blood flow sensors; pH sensors; pressuresensors; other sensors and combinations thereof. In a preferredembodiment, catheter 200 of FIG. 25 is configured to transition betweentwo asymmetric deflection geometries as has been described in referenceto numerous figures above.

Referring now to FIGS. 26A, 26B, 26C and 26D, symmetrically andasymmetrically bending shafts of the present invention are illustrated.Each of the shafts can include multiple functional elements, such aselectrodes, in the deflecting portion. Each of the shafts also caninclude an additional functional element located at the distal end ofshaft 110. FIG. 26A depicts a preferred symmetrically deflecting shaft110 which can deflect in a curve in two directions with the samegeometry (e.g., deflect with a curve of approximately 24 mm). FIG. 26Bdepicts a preferred symmetrically deflecting shaft 110 which can deflectin a curve larger than that of FIG. 26A, in two directions with the samegeometry (e.g., deflect with a curve of approximately 28 mm). FIG. 26Cdepicts a preferred asymmetrically deflecting shaft 110 which deflectsin a smaller curve in a first direction (e.g., deflect with a curve ofapproximately 24 mm) and in a larger curve in a second direction (e.g.,deflect with a curve of approximately 28 mm). FIG. 26D depicts apreferred asymmetrically deflecting shaft 110 which deflects withdifferent geometries than that described above, such as in anapproximately 28 mm curve in a first direction and in an approximately38 mm curve in a second direction.

It should be understood that numerous other configurations of thesystems, devices and methods described herein can be employed withoutdeparting from the spirit or scope of this application. Numerous figureshave illustrated typical dimensions, but it should be understood thatother dimensions can be employed which result in similar functionalityand performance.

It should be understood that the system includes multiple functionalcomponents, such as the RF generator and various ablation catheters ofthe present invention. A preferred ablation catheter consists of acatheter shaft, a shaft ablation assembly including at least one shaftablation element, and a distal ablation assembly including at least onetip ablation element.

The ablation catheters of the present invention may include a steerableouter sheath, or may work in conjunction as a system with a separatesteerable outer sheath. One or more tubular components of the ablationcatheter may be steerable such as with the inclusion of a controllablepull wire at or near the distal end. The ablation catheters of thepresent invention may be inserted over the wire, such as via a lumenwithin one of the tubular conduits such as within a lumen of the tubularbody member or control shaft, or alternatively the catheter may includea rapid exchange sidecar at or near its distal end, consisting of asmall projection with a guidewire lumen therethrough. A guidewire lumenmay be included solely for the guidewire, or may provide other functionssuch as a vacuum lumen for an integral suction port integrated at thedistal portion of the carrier assembly.

The ablation catheters of the present invention include one or moreablation elements. In preferred embodiments, one or more ablationelements are electrodes configured to deliver RF energy. Other forms ofenergy, alternative or in addition to RF, may be delivered, includingbut not limited to: acoustic energy and ultrasound energy;electromagnetic energy such as electrical, magnetic, microwave and radiofrequency energies; thermal energy such as heat and cryogenic energies;chemical energy; light energy such as infrared and visible lightenergies; mechanical energy; radiation; and combinations thereof. The RFgenerator of the present invention may further provide one of theadditional energy forms described immediately hereabove, in addition tothe RF energy.

One or more ablation elements may comprise a drug delivery pump or adevice to cause mechanical tissue damage such as a forwardly advanceable spike or needle. The ablation elements can deliver energyindividually, in combination with or in serial fashion with otherablation elements. The ablation elements can be electrically connectedin parallel, in series, individually, or combinations thereof. Theablation catheter may include cooling means, such as fins or other heatsinking geometries, to prevent undesired tissue damage and/or bloodclotting. The ablation elements may be constructed of various materials,such as plates of metal and coils of wire for RF energy delivery. Theelectrodes can take on various shapes including shapes used to focusenergy such as a horn shape to focus sound energy, and shapes to assistin cooling such as a geometry providing large surface area. Wires andother flexible conduits are attached to the ablation elements, such aselectrical energy carrying wires for RF electrodes or ultrasoundcrystals, and tubes for cryogenic delivery.

The ablation catheter of the present invention preferably includes ahandle activating or otherwise controlling one or more functions of theablation catheter. The handle may include various knobs or levers, suchas rotating or sliding knobs which are operably connected to advanceableconduits, or are operably connected to gear trains or cams which areconnected to advanceable conduits. These controls, such as knobs use todeflect a distal portion of a conduit, or to advance or retract thecarrier assembly, preferably include a reversible locking mechanism suchthat a particular tip deflection or deployment amount can be maintainedthrough various manipulations of the system.

The ablation catheter may include one or more sensors, such as sensorsused to detect chemical activity; light; electrical activity; pH;temperature; pressure; fluid flow or another physiologic parameter.These sensors can be used to map electrical activity, measuretemperature, or gather other information that may be used to modify theablation procedure. In a preferred embodiment, one or more sensors, suchas a mapping electrode, can also be used to ablate tissue.

Numerous components internal to the patient, such as the ablationelements, catheter shaft, shaft ablation assembly, distal ablationassembly, carrier arms or carrier assembly, may include one or moremarkers such as radiopaque markers visible under fluoroscopy, ultrasoundmarkers, magnetic markers or other visual or other markers.

Selection of the tissue to be ablated may be based on a diagnosis ofaberrant conduit or conduits, or based on anatomical location. RF energymay be delivered first, followed by another energy type in the samelocation, such as when a single electrode can deliver more than one typeof energy, such as RF and ultrasound energy. Alternatively oradditionally, a first procedure may be performed utilizing one type ofenergy, followed by a second procedure utilizing a different form ofenergy. The second procedure may be performed shortly after the firstprocedure, such as within four hours, or at a later date such as greaterthan twenty-four hours after the first procedure. Numerous types oftissue can be ablated utilizing the devices, systems and methods of thepresent invention. For example, the various aspects of the inventionhave application in procedures for ablating tissue in the prostrate,brain, gall bladder, uterus, other organs and regions of the body, and atumor, preferably regions with an accessible wall or flat tissuesurface. In the preferred embodiment, heart tissue is ablated, such asleft atrial tissue.

In another preferred embodiment of the system of the present invention,an ablation catheter and a heat sensing technology are included. Theheat sensing technology, includes sensor means that may be placed on thechest of the patient, the esophagus or another area in close enoughproximity to the tissue being ablated to directly measure temperatureeffects of the ablation, such as via a temperature sensor, or indirectlysuch as through the use of an infrared camera. In these embodiments, theRFG includes means of receiving the temperature information from theheat sensing technology, similar to the handling of the temperatureinformation from thermocouples of the ablation catheters. Thisadditional temperature information can be used in one or more algorithmsfor power delivery, as has been described above, and particularly as asafety threshold which shuts off or otherwise decreased power delivery.A temperature threshold will depend on the location of the heat sensingtechnology sensor means, as well as where the ablation energy is beingdelivered. The threshold may be adjustable, and may be automaticallyconfigured.

Numerous kit configurations are also to be considered within the scopeof this application. An ablation catheter is provided with one or moretip electrodes, one or more shaft electrodes and a shaft with adeflectable distal portion, such as an asymmetrically deflectable distalportion.

Though the ablation device has been described in terms of its preferredendocardial and percutaneous method of use, the ablation elements may beused on the heart during open heart surgery, open chest surgery, orminimally invasive thoracic surgery. Thus, during open chest surgery, ashort catheter or cannula carrying the ablation elements may be insertedinto the heart, such as through the left atrial appendage or an incisionin the atrium wall, to apply the ablation elements to the tissue to beablated. Also, the ablation elements may be applied to the epicardialsurface of the atrium or other areas of the heart to detect and/orablate arrhythmogenic foci from outside the heart.

As for additional details pertinent to the present invention, materialsand manufacturing techniques may be employed as within the level ofthose with skill in the relevant art. The same may hold true withrespect to method-based aspects of the invention in terms of additionalacts commonly or logically employed. Also, it is contemplated that anyoptional feature of the inventive variations described may be set forthand claimed independently, or in combination with anyone or more of thefeatures described herein. Likewise, reference to a singular item,includes the possibility that there are plural of the same itemspresent. More specifically, as used herein and in the appended claims,the singular forms “a,” “and,” “said,” and “the” include pluralreferents unless the context clearly dictates otherwise. It is furthernoted that the claims may be drafted to exclude any optional element. Assuch, this statement is intended to serve as antecedent basis for use ofsuch exclusive terminology as “solely,” “only” and the like inconnection with the recitation of claim elements, or use of a “negative”limitation. Unless defined otherwise herein, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. The breadth of the present invention is not to be limited bythe subject specification, but rather only by the plain meaning of theclaim terms employed.

What is claimed is:
 1. A medical device, the device comprising: anelongate body defining a distal end, an outer surface, and alongitudinal axis; a tip electrode coupled to the distal end of theelongate body, the tip electrode being configured to maximize heatdissipation therefrom; and at least one shaft electrode coupled to theouter surface of the elongate body.
 2. The medical device of claim 1,wherein the tip electrode defines a distal tip and at least twoflattened lateral portions.
 3. The medical device of claim 2, whereinthe distal tip of the tip electrode has a square cross section.
 4. Themedical device of claim 3, wherein the distal tip of the tip electrodedefines a flattened distal face.
 5. The medical device of claim 2,wherein the distal tip of the tip electrode is rounded.
 6. The medicaldevice of claim 5, wherein the tip electrode defines two flattenedlateral portions being approximately 180° from each other and tworounded lateral portions being approximately 180° from each other. 7.The medical device of claim 1, wherein the tip electrode defines adistal tip and a wall having a plurality of thicknesses.
 8. The medicaldevice of claim 7, wherein the distal tip of the tip electrode has awall thickness that is greater than a wall thickness of a portion of thetip electrode that is proximal to the distal tip.
 9. The medical deviceof claim 7, wherein the distal tip of the tip electrode has a wallthickness than is less than a wall thickness of a portion of the tipelectrode that is proximal to the distal tip.
 10. The medical device ofclaim 7, wherein the tip electrode defines a fin that extends from aninner surface of the tip electrode toward the longitudinal axis.
 11. Amedical device, the device comprising: an elongate body defining adistal end, an outer surface, and a longitudinal axis; a tip electrodecoupled to the distal end of the elongate body; and at least two shaftelectrodes coupled to the outer surface of the elongate body, each ofthe at least two shaft electrodes being configured to maximize heatdissipation therefrom.
 12. The medical device of claim 11, wherein theat least two shaft electrodes include a first shaft electrode and asecond shaft electrode, each of the first and second shaft electrodeshaving a helical shape.
 13. The medical device of claim 12, wherein thefirst and second shaft electrodes are configured to transmit unipolarenergy and to transmit bipolar energy.
 14. The medical device of claim13, wherein the first and second shaft electrodes record bipolarelectrograms.
 15. The medical device of claim 13, wherein each of the atleast two shaft electrodes is a partial band electrode that surroundsless than an entire circumference of the outer surface of the catheterbody.
 16. The medical device of claim 15, wherein the at least twopartial band electrodes are configured to create a plane of preferentialbending of the catheter body.
 17. The medical device of claim 11,wherein each of the at least two shaft electrodes is a band electrodedefining a wall having a plurality of thicknesses.
 18. The medicaldevice of claim 17, wherein each of the at least one shaft electrodesincludes a distal end and a proximal end, the distal end having a wallthickness that is greater than a wall thickness of the proximal end. 19.The medical device of claim 11, wherein each of the at least two shaftelectrodes has an S-shaped cross section.
 20. A medical device, thedevice comprising: an elongate body defining a distal end and an outersurface; a tip electrode coupled to the distal end of the elongate body,the tip electrode defining a distal tip and at least two flattenedlateral portions; and at least two shaft electrodes coupled to the outersurface of the elongate body, each of the at least two shaft electrodeshaving an S-shaped cross section.